Elevated height wheelchair

ABSTRACT

Embodiments of the present disclosure include a wheelchair configured to reposition an occupant between a lowered and a raised position. The wheelchair can include a frame, a seat moveable relative to the frame, a drive wheel, and one or more pairs of arm assemblies. The arm assembly includes a wheel configured to move from a first spatial location when the wheel chair is operating on flat, level ground to a second spatial location that is different than the first spatial location. Arm limiters that can selectively engage the arm assembly dependent on the position of the arm assembly and surface conditions of ground and can limit the range of motion of the arm assembly and sometimes other operational aspects of the chair.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/152,477, filed Oct. 5, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/431,441, filed Feb. 13, 2017, now U.S. Pat. No.10,130,532 issued Nov. 20, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/571,954. Filed Dec. 16, 2014, now U.S. Pat. No.9,566,200, issued Dec. 16, 2014, which claims the benefit of andpriority to U.S. Provisional Application No. 61/916,500, filed Dec. 16,2013, and U.S. Provisional Application No. 61/938,880, filed Feb. 12,2014. The entire contents of each application listed in this paragraphare incorporated by reference into this application for all purposes.

TECHNICAL FIELD

The present application relates to a wheelchair, and in particular to apower wheelchair configured to operate at least in an elevated modewhere an occupant is elevated.

BACKGROUND

Wheelchairs are an important means of transportation for a significantportion of society. Whether manually propelled or powered, wheelchairsprovide an important degree of independence for those they assist.However, this degree of independence can be limited if the wheelchair isrequired to traverse obstacles such as, for example, curbs that arecommonly present at sidewalks and other paved surface interfaces, anddoor thresholds. Accordingly, power wheelchairs have been the subject ofincreasing development efforts to provide handicapped and disabledpersons with independent mobility to assist them in leading even morenormal and active lives.

To aid in climbing curbs, some power wheelchairs typically have a pairof forward extending anti-tip assemblies that are rotatably coupled tothe wheelchair frame. The arm members of the anti-tip assemblies arerotatably coupled to the wheelchair frame such that when the wheelchairencounters a curb, the anti-tip assemblies will pivot upwardly tothereby allow the wheelchair to traverse the curb. Some powerwheelchairs also have elevatable seats that permit the occupant to moveat “eye-level” with persons walking with them. However, wheelchairsoperating with seats at elevated positions are susceptible toinstability under certain conditions, and anti-tip assemblies, whilebeneficial for climbing obstacles such as curbs, may contribute to theinstability when the wheelchair is operating on other than flat, levelground.

SUMMARY

Embodiments of the present disclosure include a wheelchair configured toreposition an occupant between a lowered and a raised position. Thewheelchair can include a frame, a seat moveable relative to the frame, adrive wheel, and one or more pairs of arm assemblies. The arm assemblyincludes a wheel configured to move from a first spatial location whenthe wheel chair is operating on flat, level ground, to a second spatiallocation that is different than the first spatial location. Arm limiterscan selectively engage the arm assembly based on at least one of a seatposition, position of the arm assembly, and surface conditions ofground. The arm limiters can limit the range of motion of the armassembly and sometimes other operational aspects of the chair.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofexample embodiments of the application, will be better understood whenread in conjunction with the appended drawings, in which there is shownin the drawings example embodiments for the purposes of illustration. Itshould be understood, however, that the application is not limited tothe precise systems and methods shown. In the drawings:

FIG. 1 is a top perspective view of a powered wheelchair in accordancewith an embodiment of the present disclosure;

FIG. 2A is a side elevation view of the powered wheelchair shown in FIG.1, with a portion of the seat removed and illustrating the seat in araised position;

FIG. 2B is a side elevation view of the powered wheelchair shown in FIG.2A, showing the seat in the lowered position;

FIG. 3A is a side elevation view of the powered wheelchair shown in FIG.2B, with a drive wheel removed to illustrate a forward arm assembly andan arm limiter according to an embodiment of the present disclosure;

FIG. 3B is a rear perspective of a portion of the powered wheelchairshown in FIG. 3A;

FIG. 4A is a side elevation view of a portion of the powered wheelchairshown in FIG. 3A, illustrating the arm limiter in the lockedconfiguration;

FIG. 4B is a side elevation view of a portion of the powered wheelchairshown in FIG. 3A, illustrating the arm limiter in an open configuration;

FIG. 4C is a side elevation view of a portion of the powered wheelchairshown in FIG. 3A, illustrating the arm limiter that is blocked fromtransitioning into the locked configuration as the powered wheelchairtraverses an obstacle;

FIG. 5 is a block diagram illustrating a control system for operatingthe powered wheelchair illustrated in FIGS. 1 through 4C, according toan embodiment of the present disclosure;

FIGS. 6A and 6B are process flow diagrams illustrating operation ofpowered wheelchair in standard operating mode and an elevated motionmode (a portion of the diagram is shown in FIG. 6A and another portionof the diagram is shown in FIG. 6B);

FIG. 7 is a perspective view of an arm limiter assembly for the poweredwheelchair according to another embodiment of an aspect of the presentdisclosure;

FIGS. 8A-8D are sides views of rotatable members according toalternative embodiments of aspects of the present disclosure;

FIG. 9A is a side elevation view of a powered wheelchair according toanother embodiment of an aspect of the present disclosure, illustratingthe arm limiter shown FIG. 7;

FIG. 9B is a side elevation view of a portion of the powered wheelchairshown in FIG. 9A, illustrating the front wheel ascending an obstacle;

FIG. 10A is a side elevation view of a powered wheelchair according toanother embodiment of an aspect of the present disclosure, illustratingthe arm limiter in the locked configuration;

FIG. 10B is a side elevation view of a portion of the powered wheelchairshown in FIG. 10A, illustrating the arm limiter in an openconfiguration;

FIG. 10C is a side elevation view of a portion of the powered wheelchairshown in FIG. 10A, illustrating the arm limiter being inhibited fromtransitioning into the locked configuration as the powered wheelchairascends an obstacle;

FIG. 10D is an enlarged view of a plate of the arm limiter assemblyshown in FIG. 10B;

FIG. 11A is a schematic side elevation view of a powered wheelchairaccording to another embodiment of an aspect of the present disclosure,illustrating an arm limiter in the locked configuration;

FIG. 11B is an end view of the arm limiter illustrated in FIG. 11A;

FIG. 12A is a schematic side elevation view of a powered wheelchairaccording to another embodiment of the present disclosure, illustratingthe arm limiter in the locked configuration;

FIG. 12B is a side elevation view of a portion of the powered wheelchairshown in FIG. 12A, illustrating the arm limiter in an open configurationwith a portion thereof retracted;

FIG. 12C is a side elevation view of a portion of the powered wheelchairshown in FIG. 12A, illustrating the arm limiter being inhibited fromtransitioning into the locked configuration as the powered wheelchairascends an obstacle;

FIG. 13A is a schematic side elevation view of a portion of a poweredwheelchair according to another embodiment of the present disclosure,illustrating a rear arm assembly and a rear arm limiter assembly in anopen configuration;

FIG. 13B is a side elevation view of a portion of the powered wheelchairshown in FIG. 13A, illustrating the rear arm limiter assembly beinginhibited from transitioning into the locked configuration as thepowered wheelchair descends an obstacle;

FIG. 14A is a schematic side elevation view of a portion of the poweredwheelchair, illustrating the arm assembly on flat, level ground and anarm limiter assembly in an open configuration; and

FIG. 14B is a side elevation view a portion of the powered wheelchairshown in FIG. 14A, illustrating the arm assembly translated upwardly asthe powered wheelchair ascends an obstacle.

FIG. 15A is a schematic side elevation view of a portion of a poweredwheelchair according to another embodiment of an aspect of the presentdisclosure, illustrating an arm limiter assembly in an openconfiguration;

FIG. 15B is a side elevation view a portion of the powered wheelchairshown in FIG. 15A, illustrating the arm assembly ascending an obstacleand the arm limiter in a locked configuration;

FIG. 15C is a side elevation view a portion of the powered wheelchairshown in FIG. 15A, illustrating the arm attempting to ascend an obstacleand with arm limiter in another locked configuration;

FIG. 16A is a schematic side elevation view of a portion of a poweredwheelchair according to another embodiment of an aspect of the presentdisclosure, illustrating the arm limiter in the locked configuration;and

FIG. 16B is a side elevation view a portion of the powered wheelchairshown in FIG. 15A, illustrating the arm assembly translated upwardly asthe powered wheelchair ascends an obstacle.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to FIGS. 1-2B, an embodiment of the present disclosureincludes a wheelchair 10 configured to elevate a seat 22 between aconventional lowered position and a raised position that allows anoccupant to operate the wheelchair 10 with the seat at the raisedposition, which in some circumstances can be at a conversational heightwith others. The wheelchair 10 may be a powered wheelchair. In someembodiments, wheelchair 10 is configured to selectively limit certainoperational aspects when, for example, the wheelchair 10 is in theprocess of traversing an obstacle, is on un-level ground, and/or whenthe seat is raised. Likewise, the wheelchair 10 may prevent the raisingof the seat when the wheelchair is climbing an obstacle or is on unlevelground. An “obstacle” as the term is used herein includes any relativelyraised or lowered structure on the ground surface G that the wheel mustascend or descend to cross over. Operating a wheelchair when the seat isin the raised position can create instability, especially when climbingcurbs or transitioning to a descent when appropriate safety features arenot deployed. For instance, when the seat is in the fully raisedposition, the center of gravity of the occupied wheelchair is elevatedand/or shifted forward or rearward (depending, for example, on the liftmechanism associated with the chair). The risk of tipping can increaseon an incline and overall wheelchair stability can be compromised,especially when traversing or attempting to traverse an obstacle. Thewheelchair 10 as described herein improves stability when the seat 22 isin the raised position and the individual is at a conversational height.As a result of improved stability chair travelling speeds can beincreased. Increased traveling speeds may include walking speeds,jogging speeds or running speeds. Conversational height as used hereinrefers to when the occupant is elevated above the ground surface G tomake communication with others (e.g., average height adult males orfemales) standing or walking next to wheelchair easier. For example,conversational height could be “eye-level.”

The powered wheelchair 10 includes a frame 14, a pair of drive wheels 32coupled to the frame 14 and driven by at least one drive motor 34 (FIG.2A). A pair of anti-tip arm assemblies 38 extend from the frame 14 in aforward direction F relative to the drive wheels 32. A pair of rear armassemblies 48 extend from the frame 14 in a rearward direction R that isopposite to the forward direction F. As used herein the forward-rearwarddirection F-R may refer the horizontal direction when the wheelchair isoperating on flat, level ground. In accordance with the illustratedembodiment, the power wheelchair 10 is a mid-wheel drive wheel chair andincludes front wheels 46 and rear wheels 49 disposed in the forward andrearward directions F and R relative to the drive wheels 32,respectively. The drive motor 34 causes the drive wheels 32 to rotateabout the drive wheel axis A2 to advance the wheelchair along thesurface G. The front wheel 46 is rotatable about the front wheel axis A1and the rear wheel 47 is rotatable about the rear wheel axis A3. Thepresent disclosure, however, is not limited to mid-wheel powered wheelchairs.

The powered wheel chair 10 also includes a lift mechanism 18 mounted tothe frame 14 with the seat 22 supported by the lift mechanism 18. Thelift mechanism 18 is configured to, in response to inputs an occupantapplies to an input device 8, move the seat 22 between a loweredposition 5L (FIGS. 1 and 2B) and a raised position 5R (FIG. 2A)generally along a vertical direction V that is perpendicular the forwardand rearward directions F and R. While a scissor-type lift mechanismthat is actuated by a lead screw mechanism is illustrated and describedbelow, any type of lift mechanism may be employed. Further, the poweredwheelchair can be configured to move the seat into the raised positionand tilt the seat base and seat back relative to each other in theraised position. In an embodiment, the powered wheelchair can include alift and tilt mechanism, such as the lift and tilt mechanism disclosedin U.S. Patent App. Pub. No. 2014/0262566, entitled “Lift Mechanism AndTilt Mechanism For A Power Wheelchair,” incorporated by reference hereinin its entirety.

The powered wheel chair 10 also includes one or more arm limiterassemblies 60, shown for example in FIG. 3A, coupled the frame 14 andconfigured to selectively engage the anti-tip assemblies 38 so as toinhibit relative motion between the anti-tip assemblies 38 and frame 14in certain instances during operation of the wheelchair 10. An armlimiter assembly as used herein may be referred to as an arm limiter orlimiter. Preventing relative motion between anti-tip assemblies 38 andthe frame 14 can limit certain operations of the wheelchair 10 in orderto improve stability and occupant safety. The arm limiter assemblies 60transition between a first or disengaged configuration and a second orlocked configuration where operation of the anti-tip assemblies 38 arelimited. Further, operation of arm limiter assemblies 60 may be limited,inhibited, impaired or delayed when the wheelchair is traversing anobstacle. For instance, the arm limiter assemblies 60 may not transitioninto locked configuration if the anti-tip assemblies are alreadyattempting to traverse an obstacle, as will be further discussed below.For just one instance, operation of the lift mechanism 18 can be limitedso that the seat cannot be moved to the raised position when thewheelchair is climbing an obstacle or descending along an incline. Thepowered wheelchair 10 is configured to safely operate in a mode wherebythe seat 22 of the wheelchair 10 is raised to a raised position at theconversational height with walking companions and the wheelchair 10 iscapable of safely advancing along the surface G, for instance a normalspeed, such as normal walking speed.

The power wheelchair 10 has different operational modes, such as astandard mode and one or more elevated motion modes. In someembodiments, a control system 90 (FIG. 5) includes a controller 92configured to operate the wheelchair 10 in the different operationalmodes, an input device 8 in electronic communication with the controller92, and a plurality of sensors 96 a-96 c in electronic communicationwith the controller 92. The controller 92 is responsive to inputs fromthe input device 8 and one or more of the sensors 96 a-96 c in order tocause the powered wheelchair 10 to operate at least in (i) a standardmode when the seat 22 is in the lowered position such that thewheelchair is moveable along the surface G in accordance with standarddrive parameters (that is, conventional parameters that are not limitedfor elevated seat operation), and (ii) one or more elevated motion modeswhereby the seat is in the raised position and drive parameters arelimited to some extent. The elevated motion modes may include A) a firstor normal elevated motion mode where the wheelchair is capable operatingaccording to a first set of limited drive parameters, and B) a secondelevated motion mode (sometimes referred to as an elevated-inhibitedmode) whereby the wheelchair 10 is capable of operating according to asecond set of limited drive parameters that have limits that aretypically less than upper limits of the first set of limited driveparameters. The phrase “drive parameters” as used herein (whether instandard or elevated modes) include at least a speed (miles/hr),acceleration, and deceleration of the wheelchair. In some embodiments,the drive parameters include directional components, such as forwardspeed, reverse speed, and turn speed, forward acceleration, forwarddeceleration, reverse acceleration, and reverse deceleration. Forbrevity and ease of illustration, the standard and elevated modes beloware described with reference to the speed of the wheelchair. However, itshould be appreciated that the ranges and limits discussed below withrespect to speed are applicable to the other drive parameters such asturn speed, acceleration, and deceleration described above.

In accordance with the illustrated embodiment, the standard mode is whenthe seat 22 is in the lowered position such that the wheelchair ismoveable along the surface G at typical wheelchair speeds. The firstelevated motion mode can be when the wheelchair is capable of moving ata first speed range, up to a maximum raised-seat drive speed, which isless than the typical wheelchair speeds. The second elevated motion mode(or an elevated-inhibited mode) is when the wheelchair 10 is capable ofmoving at a second elevated mode speed range, up to a maximumraised-inhibited drive speed that is less than the upper limit of thefirst speed range.

In the standard mode the wheelchair can move at a standard orlowered-seat drive speed range that is typical of conventionalwheelchairs, such as between 0.0 mph and about 10.0 mph. Accordingly, itshould be appreciated that the fully lowered-seat drive speed can havean upper limit that is anywhere in the conventional range of between apractical minimum (or at rest at 0 mph) and, for example, 10.0 mph asindicated. Furthermore, it should be appreciated that when thewheelchair is operating in the standard mode, the wheelchair 10 can beconfigured to move at any speed as desired and is not limited to a speedthat is between the practical minimum and 10.0 mph. The poweredwheelchair 10 would typically be in the standard mode (that is, with theseat in the fully-lowered position) when the wheelchair is traversingobstacles O (FIG. 4C) such as a curb. The term “standard mode” includesa mode that has no speed restrictions by the controller that are relatedto seat position.

When in the elevated motion modes, the wheelchair 10 can be configuredto move at a speed that has a limit that is less than the standard modedrive speed upper limit. In the elevated motion modes, the powerwheelchair preferably is capable of moving at a walking speed (orperhaps faster) while seat 22 is in the raised position such that theoccupant is at the conversational height with a person walking next thepowered wheelchair. In an exemplary embodiment, when in the normalelevated motion mode, the first speed range is between a practicalminimum and 5.0 mph, preferably between the practical minimum and 3.75mph. That is, the wheelchair 10 can be configured to move at a maximumraised-seat drive speed that is no more than 5.0 mph, preferably no morethan 3.75 mph. It should be appreciated that the raised-seat drive speedcan have an upper limit that is anywhere between first speed range ofthe practical minimum to 5.0 mph. Furthermore, when the wheelchair 10 isoperating in the normal elevated motion mode, there may be circumstancesin which the upper limit may be set higher than 5.0 mph. The term“practical minimum” speed as used herein means that the lower limit ofthe range is chosen according to the parameters understood by personsfamiliar with power wheelchair structure and function, and may be closeto zero mph under some conditions.

In an instance in which wheelchair 10 is operating in the elevatedmotion mode, and at least one safety criteria is not met, the controllerwill cause the wheelchair 10 to operate in some mode other than thefirst, normal elevated motion mode. For example, the controller maycause the wheelchair 10 to operate in the second elevated motion mode orelevated inhibited mode at least until all of the safety criteria aremet. For example, in some embodiments, if the seat 22 is in the raisedposition and one of the safety criteria is not met, the controller willallow the wheelchair 10 to move within the second, elevated-inhibitedspeed range, up to the reduced maximum raised-inhibited speed that isless then maximum raised-seat drive speed. The maximum raised-inhibiteddrive speed can be a speed that is no more than 3.0 mph, preferably nomore than 1.5 mph. It should be appreciated, however, that theraised-inhibited drive speed can have any upper limit as desired so longas it is less than an upper limit of the first, normal speed range.

Accordingly, in order for the wheelchair 10 to operate in the elevatedmotion modes, certain safety criteria should be satisfied as will bediscussed further below. The sensors 96 a-96 c can collectively detectinformation indicative of when the wheelchair 10 is in a position tosafely operate in the elevated motion modes. If the sensors 96 a-96 cdetect a condition that indicates that it is not safe to operate thewheelchair in the elevated motion mode, the controller 92 will operatethe wheelchair 10 in some other mode such as the elevated inhibited modeor standard mode (that is, by requiring the seat to be in the lowermostposition). In certain instances, for example, the wheelchair 10 will notoperate in the elevated motion modes, i.e., the seat 22 will not moveinto the raised position if the seat 22 is initially in the loweredposition and the wheelchair 10 is ascending an obstacle or descendingdown an incline.

Turning to FIGS. 2A-2B, the frame 14 supports the drive wheels 32,anti-tip assemblies 38, rear assemblies 48, the lift mechanism 18 andseat 22. As illustrated, the frame 14 includes a front end 14 f, a rearend 14 r spaced from the front end 14 f in a forward direction F, abottom 15 b, and a top 15 t spaced from the bottom 15 b in the verticaldirection V. The frame 14 further supports one or more batteries 36 aand 36 b, the drive motors 34, and various control modules that are usedto operate the powered wheelchair.

The lift mechanism 18, in some embodiments, includes left and right ofscissor assemblies 16 operatively connected to frame 14, a lift motor20, and a lift control system (which preferably is integrated with thecontroller described herein) that can be used to impart a lifting forceand rate by which the seat 22 moves from the lowered position to theraised position. One scissor assembly will be described below for easeof illustration. The other scissor assembly is constructed similarly.The scissor assembly 16 includes first and second scissor bars 17 and 19that extend between the seat 22 and the frame 14 and are rotatablycoupled to each other. The first scissor bar 17 has an upper end 17 ufixed to the seat 22 and a lower end 17 l that is moveably coupled tothe top 15 t of the frame 14. For instance, the lower end 17 l can bemovably coupled to a support rack 14 s attached to or extendingmonolithically from the top 15 t of the frame 14. The second scissor bar19 includes an upper end 19 u that is moveably coupled to the seat 22.As illustrated, the upper end 19 u extends partly into an elongate slot21 defined in the seat frame 23 a. The lower end 19 l of the scissor bar19 is fixed to the frame 14, for instance to the support rack 14 s.

The motor 20 is operatively coupled to the lower end 17 l of the scissorbar 17 and is configured to cause the lower end 17 l to translate alongthe frame 14 in the forward and rearward directions F and R. The liftmotor 20 is operativly coupled to a drive actuator, such as a threadedshaft, that is connected to the lower end 17 l of the scissor bar 17.For instance, a threaded nut (not shown) is fixed, directly orindirectly, to the lower end 17 l and the drive screw extends throughthe threaded nut. Operation of the motor turns the drive screw in thedrive nut, which causes translation of the lower end 17 l to advancealong the drive screw depending on rotational direction of the drivescrew. In operation, when the seat is raised, the lower end 17 l of thescissor bar 17 is disposed toward the central region of the frame 14 andwhen the seat 22 is in the lowered position, the lower end 17 l of thescissor bar 17 is has translated closer to the rear end 14 r of theframe 14. As the lower end 17 l translates along the frame 14, the upperend 19 u of the second scissor bar 19 translates along the elongatedslot 21 of the seat 22 as the seat 22 is lowered toward the frame 14.The seat 22 is a seat assembly that includes a base, a seat back (baseand seat back not numbered or shown in FIGS. 2A and 2B), seat frame 23 athat supports the base. The seat frame 23 a defines a seat bottom 23 bthat faces the frame 14. The distance D extends from the top 15 t of theframe 14 to the bottom 23 b of the seat 22 along a vertical direction V.The distance D increases as the seat 22 is moved from the loweredposition 5L to the raised position 5R, and decreases the seat 22 ismoved from the raised position 5R to the lowered position 5L. The liftmechanism illustrated is exemplary only. And it should be appreciatedthat the lift mechanism is not limited to scissor-type mechanisms or theuse of screw-type actuators as described above.

Turning to FIGS. 3A and 3B, as noted above, the wheelchair 10 includes apair of anti-tip arm assemblies 38. For ease of illustration only oneanti-tip arm assembly 38 will be described below. The other anti-tipassembly 38 in the pair preferably has the same structure but orientedon the opposite hand. The anti-tip arm assembly is also referred to inthis disclosure as an arm assembly 38. The arm assembly 38 includes anarm member 42 moveably coupled to the frame 14, a front wheel 46 coupledto the arm member 42, and at least one stop member 44 a disposed alongthe arm member 42. In the illustrated embodiment, the arm member 42includes an arm body 43 a that defines an arm proximal end 43 p and anarm distal end 43 d spaced from the arm proximal end 43 p along an armbody axis 45. The arm member body 43 a is curved along the arm axis 45such that distal end 43 d is spaced a greater vertical distance from thesurface G compared to the vertical distance that the proximal end 43 pis spaced from the surface G. The curved arm body 43 a provide clearancefor the wheel assembly. It should be appreciated that the arm memberbody 43 a could be linear along the arm axis 45 in other embodiments.The distal end 43 d of the arm member 42 includes a distal housing (notnumbered) that receives a front wheel assembly 46. The proximal end 43 pdefines a proximal housing (not numbered) that holds and/or defines aconnector (not numbered) that is coupled to the frame 14. The arm memberbody 43 a can be any structure, such as an elongate tube, bar, rod orplate and may or may not have uniform or substantially uniform crosssection between proximal end 43 p and distal end 43 d. As illustrated,the arm member body 43 a is tubular and is exemplary only. In otherembodiments, the arm member body 43 a can be or may include a bar orplate with a substantially rectilinear cross-section perpendicular thearm axis 45. The arm member 42 can be formed of multiple components thatare connected together with fasteners or welds, or pivotally attachedtogether, without limitation. In other embodiments, the arm member bodycan be a monolithic structure, such as a cast or extruded material.

The front wheel 46 is coupled to the distal end 43 d and is rotatableabout the front wheel axis A1. As illustrated, the front wheel 46 is incontact with ground or surface G during normal operation. The distal end43 d of arm member includes a caster assembly (not numbered) supportedby the distal housing. The caster assembly rotatably couples the frontwheel 46 to the arm member 42 such that wheel 46 is rotatable about anaxis (not shown) that is normal to the ground surface G andperpendicular the wheel axis A1. It should be appreciated, however, thatin some embodiments, the front wheel 46 can be an anti-tip wheel that israised or otherwise spaced from the ground or surface G during normaloperation in a configuration that does not include a caster. The term“anti-tip” wheel as used herein encompasses caster wheel assemblies(such as front wheel 46) and anti-tip wheels that are raised duringnormal operation and encompasses wheels in the front and the rear of thewheelchair. In such embodiments, the raised anti-tip wheels can have afirst or rest position 40 a when the wheelchair 10 is operating on flat,level ground.

Continuing with FIGS. 3A and 3B, the arm assembly 38 is coupled to theframe 14 and configured to move the wheel 46 relative to the frame 14upon encountering an obstacle. The arm assembly 38 illustrated in FIGS.3A and 3B is pivotably coupled the frame 14 such that the arm assembly38 and wheel axis A1 pivots about the pivot axis P1. It should beappreciated, however, that the arm assemblies can be coupled to theframe 14 such that the arm member 42 and wheel axis A1 translatesrelative to the frame 14, e.g. as illustrated in wheelchair 610 shown inFIGS. 14A and 14B. Accordingly, the powered wheelchair is configuredsuch that the spatial location of the arm member 42 and front wheel axisA1 are moveable, rotationally and/or translatably (e.g., relative to theframe and/or drive axis as opposed to spinning about its axle or casterkingpin). The words “move,” “moveable”, or “movement” when used inreference to motion of the arm member and front wheel includesrotational movement (FIGS. 3A and 3B) and translational movement (FIGS.14A and 14B) (and is not intended to include rotation about a frontwheel axis A1 or wheel axle.

In the embodiment illustrated in FIGS. 3A and 3B, the arm assembly 38 iscoupled to the frame 14 and configured to pivot such that the arm member42 and wheel axis A1 is pivotable about the axis P1 along a rotationaldirection B1-B2. For instance, the arm assembly 38 is configured topivot about the pivot axis P1 as the wheelchair 10 traverses obstaclesalong the surface G, such as a curb. The arm assembly 38 is configuredso that arm member 42 is in a first or rest position 40 a relative tothe frame 14 when the wheelchair 10 is operating on flat, level ground(that is, “normal operation”). When the wheelchair encounters anobstacle, the arm member 42 pivots upwardly about axis P1 in a first orupward rotational direction B1 toward a second position 40 b that isdifferent from the first position 40 a. In this regard, the secondposition 40 b is different from the first position 40 a along 1) boththe vertical direction V and the forward-rearward direction F-R, or 2)only the vertical direction V. When the front wheel 46 encounters adescent down a curb, however, the arm member 42 pivots downwardly aboutthe axis P1 in a second or downward rotational direction B2 that isopposite the first rotational direction B1 (which movement below groundG is not shown in the figures). The second position 40 b as used hereincan mean a position that is different from the first position 40 a in anupward or downward direction. When viewing the figures, the firstrotational direction is clockwise and the second rotational direction iscounterclockwise. The extent that the arm member 42 pivots about thepivot axis P1 is referred to herein as the range of rotation or range ofmotion as further described below. Further, while reference is made tothe arm member 42 having a first position 40 a and a second position 40b that is different than the first position 40 a, the first and secondpositions 40 a and 40 b also refer to the relative locations of thewheel axis A1 when encountering an obstacle. In regard, it should beappreciated that the wheel axis A1 can be repositioned from a firstposition 40 a into a second position 40 b.

As noted above, the arm assembly can be configured such that the armmember 42 and wheel axis A1 is translatable between the first position40 a to the second position 40 b. For example, as illustrated in FIGS.16A and 16B, arm assemblies 638 are coupled to the frame 14 such thatthe arm member 42 and wheel axis A1 is translatable between the firstposition 40 a and the second position 40 b along a linear direction Cthat is offset with respect to the vertical direction V andforward-rearward direction F-R. In such an embodiment, the secondposition 40 b is different from the first position 40 a along 1) thevertical direction V or the forward-rearward direction F-R. Operation ofthe wheel chair 610 and arm assembly 638 is further detailed below. Thetranslating arm assemblies 638 can be similar to the arm assembliesdisclosed in U.S. Pat. No. 7,232,008, entitled, “Active anti-tip wheelsfor power wheelchair,” (the 008 patent) assigned to Pride MobilityProducts Corporation. The disclosure of the 008 patent is incorporatedby reference herein.

Continuing with FIGS. 3A and 3B, the proximal end 43 p of the arm member42 is pivotably coupled to the frame 14 such that the proximal end 43 pdefines the pivot axis P1. However, the arm member 42 can be pivotablycoupled to the frame 14 at a location disposed forward from the proximalend 43 p. In other words, the pivot P1 can be defined at any locationalong the arm member 42 between the proximal end 43 p and distal end 43d. In addition, in some embodiments, the pivot axis P1 is disposed belowa line L1 (FIGS. 2A and 2B) that intersects the front wheel rotationalaxis A1 and the drive wheel rotational axis A2. The wheelchair 10 can beconsidered a “low pivot” axis type wheelchair, such as that disclosed inU.S. Pat. No. 8,181,992, (the 992 patent) entitled “Anti-tip system fora power wheelchair.” The disclosure of the 992 patent is incorporated byreference into this disclosure to define a low pivot axis type powerwheelchair. However, the wheelchair 10 is not required to be a low-pivotaxis type wheelchair.

Continuing with FIGS. 3A and 3B, the stop member 44 a is located on oris part of the arm member 42 so as to, in some circumstances, engage thearm limiter assembly 60. In the illustrated embodiment, the distancefrom the pivot axis P1 to the stop member 44 a along the arm axis 45 isless than the distance from the stop member 44 a to the distal end 43 dof the arm member 42. In certain embodiments, the position of the stopmember 44 a toward the distal end 43 d permits engagement with theillustrated arm limiter assembly 60 (when in locking configuration) whenthe front wheel 46 encounters moderately sized obstacles. However, thestop member 44 a could be disposed along any portion of the arm member42 as needed. The stop member 44 a includes a first or upper engagementsurface 44 u (FIG. 4A) on a portion of the upper side of stop member 44a. The upper engagement surface 44 u faces upwardly opposite the groundsurfaced G when the arm member 42 is in the first position 40 a. Thestop member 44 a also includes a second or rear surface 44 r (FIG. 4B)on a rearward side of stop member 44 a. The rear surface 44 r faces therearward direction R when the arm member 42 is in the first position 40a. The stop member 44 a is shown as a cylindrical body disposed alongthe arm member 42. However, the stop member 44 a can be monolithic withthe arm member body 43 a such that the arm member 42 defines the upperand rear engagement surfaces 44 u and 44 r. For instance, an upwardlyfacing surface of the arm member can define a curved or stepped profile.In certain embodiments, arm member 42 can include a projection thatdefines the stop member 44 a.

Continuing with FIGS. 3A and 3B, each arm assembly 38 can furtherinclude at least one linkage 50 that operatively connects the arm member42 to a respective drive motor 34. Motor torque from the drive motors 34will influence or cause the forward arm members 42 to pivot about theirrespective pivots P1 as the wheelchair 10 traverses an obstacle tothereby aid the wheelchair during obstacle traversal. It should beappreciated, however, that the anti-tip assemblies 38 can alternativelybe passive (i.e. not coupled to the drives) as desired.

Wheelchair 10 further includes a pair of arm limiter assemblies 60 thatare each associated with a respective arm assembly 38. Each arm limiterassembly 60 is configured to selectively inhibit the range of motion ofthe arm assembly 38 relative to the frame 14. In the illustratedembodiment (see FIGS. 3A and 3B), the arm limiter assembly 60 isconfigured to selectively inhibit the extent that the arm assembly 38,specifically the arm member 42 or wheel 46, can pivot about the pivotaxis P1 in the upward direction B1. The arm limiter assembly 60 has afirst or disengaged or open configuration as shown in FIG. 4B (shown indashed lines in FIG. 3A) in which the arm limiter assembly 60 does notrestrict the upward range of motion of arm member 42. Accordingly, inthe disengaged or open configuration, the arm assembly 38 is rotatablefrom the first position 40 a (that is, it's normal state) through afirst range of rotation about the pivot axis P1.

In addition, the arm limiter assembly 60 has a second or engaged orlocked configuration as shown in FIG. 4A (shown in solid lines in FIG.3A) in which arm limiter limits the upward range of motion of the armmember 42. In the engaged or locked configuration, the arm assembly 38is rotatable through a second range of rotation that is less than thefirst range of rotation. Accordingly, when the arm limiter assembly 60is in the locked configuration, the arm member 42 is not rotatable aboutthe pivot axis P1 to the same extent that the arm member 42 is rotatableabout the pivot axis P1 when the arm limiter assembly 60 is in the openconfiguration. The wheelchair 10 is configured to transition the armlimiter assembly 60 between the open and locked configurations based onposition of the seat 22 and/or condition of the ground surface G thatthe wheelchair 10 is traveling along, as will be further detailed below.

The range of rotation as used herein refers to rotation of the armmember 42 to a position that is different than the first position 40 a.When the arm member 42 is in the first position 40 a, such that thewheelchair 10 is operating on flat, level ground, a first, fixedreference line I1 intersects the pivot axis P1 and the front wheel axisA1. The first line I1 is coaxial with an arm reference line 12 that alsointersects the pivot axis P1 and wheel axis A1 only when the wheelchair10, for example the front wheel 46 and drive wheels 32, are on a flat,level ground surface G. The arm reference line 12 represents the firstposition 40 a of the arm assembly 38 (FIGS. 4A, 4B). The lines I1 and I2define an angle α that is about zero (0) degrees when the arm assembly38 is in the first position 40 a. In the illustrated embodiment, in thefirst range of rotation (that is, without upward limit by arm limiterassembly 60) angle α can be up to, for example, about 20 degrees ofrotation relative to the first position 40 a in either the upward(first) rotational direction B1 or the downward (second) rotationaldirection B2. The range of arm rotation when arm limiter assembly 60 isin the open configuration is bounded merely by the wheelchair structureand its corresponding function. For instance, in the first range ofrotation angle α can extend from −10 degrees (that is, in the downwarddirection) from the line I1 at the first position 40 a to +10 degrees inthe upward rotation direction B2 from the line I1 at the first position40 a.

The second range of rotation (that is, the rotation capable when the armlimiter is engaged with the arm) can be any desired range that is lessthan the first range of rotation. In the second range of rotation angleα can be, for example, up to about 10 degrees of rotation relative tothe first position 40 a in the upward (first) rotational direction B1and/or the downward (second) rotational direction B2. For instance, inthe second range of rotation angle α can extend from −5 degrees (thatis, in the downward direction) from the line I1 at the first position 40a to +5 degrees in the upward rotation direction B2 from the line I1 atthe first position 40 a. When the arm limiter assembly 60 is in thelocked configuration, the second range of rotation includes the angle αequal to about zero (0) degrees such that the arm member 42 is fixedrelative to the frame 14. In other words, the second range of rotationincludes arm member 42 fixed against pivotable movement (especiallyupward movement) relative to frame 14. It should be appreciated that thesecond range of rotation can be partially within the first range ofrotation, such the upper and lower limits are 0 degrees and +10 degrees.In the exemplary embodiment shown, the arm limiter assembly 60 isinhibited from transitioning into the second configuration when theposition of the arm assembly is rotationally different from the firstposition 40A relative to the frame 14 by more than four (4) degrees. Insome embodiments, the arm limiter assembly 60 is prevented fromtransitioning into the second configuration under selected triggerconditions of the wheelchair. One trigger configurations may includewhen the position of the arm assembly is different from the firstposition 40A relative to the frame 14 by more than one degree, twodegrees, three degrees or four or more degrees. Other trigger conditionsmay include the position of the seat, inclination of the wheelchair, andspeed of the wheelchair. In one embodiment, limiter assembly 60 isprevented from transitioning into the second configuration when theposition of the arm assembly is different from the first position 40Arelative to the frame 14 by more than one degrees. In one embodiment,limiter assembly 60 is prevented from transitioning into the secondconfiguration when the position of the arm assembly is different fromthe first position 40A relative to the frame 14 by more than twodegrees. In one embodiment, limiter assembly 60 is prevented fromtransitioning into the second configuration when the position of the armassembly is different from the first position 40A relative to the frame14 by more than three degrees. In other exemplary embodiments, the armlimiter assembly 60 is inhibited from transitioning into the secondconfiguration when the position of the arm assembly is rotationallydifferent from the first position 40A relative to the frame 14 by lessthan four (4) degrees.

Arm limiter assembly 60 is in the open configuration when the wheelchair10 is operating in the standard motion mode, i.e., when the seat is inthe lowered position. When the controller 92 receives an input from theinput device 8 to operate the wheelchair 10 in the elevated motion mode,the controller 92 causes arm limiter assembly 60 to transition into thesecond or engaged configuration. However, if certain conditions are notmet the arm limiter assembly 60 may be inhibited from moving into thesecond configuration. For example, the arm limiter assembly 60 may beable to move into the second configuration only when the front wheel 46and drive wheel 32 are on flat, level ground. Further, the arm limiterassembly 60 may be able to move into the second configuration only whenfront wheel 46 is in a different position from the first position 40 a,but still within the second range of motion as noted above. In theembodiment shown, if the front wheels 46 are on uneven ground relativeto the drive wheels 32 such that a forward arm member 42 is pivotedupwards into the second position 40 b as shown in FIG. 4C, then the armlimiter assembly 60 is physically blocked from moving into the lockingconfiguration. In alternative embodiments, the controller 92 may beconfigured to inhibit the arm limiter assembly 60 from transitioninginto the second configuration when the front wheel 46 and drive wheelare on flat, level ground.

The arm limiter assembly 60 is configured to transition between the openconfiguration and the locking configuration so as to limit the range ofrotation of the arm member 42 as described above. In the embodimentillustrated in FIGS. 3A-4C, the arm limiter assembly 60 includes arotatable member 70 that is rotatably mounted to the frame 14, anactuator 88, a transfer linkage 84 coupled to actuator 88, and a biasingmember, such as spring 80 operably connected to the linkage 84 and therotatable member 70. The actuator 88 is operable to cause movement ofthe transfer linkage 84, which in turn causes movement of the rotatablemember 70 as further detailed below.

Referring to FIG. 3B-4B, the rotatable member 70 is pivotably coupled tothe frame 14 at a connection 69 and rotatable about the pivot axis P2between the open configuration (FIG. 4B) and the locked configuration(FIGS. 3B, 4A). In the illustrated embodiment, the rotatable member 70is a beam or brace in the form of a bar. Other elongate shapes, such aswithout limitation a plate, rod, tube, are contemplated in furtherembodiments. The rotatable member 70 defines a body 74 having a first orproximal end 74 a rotatably coupled to the frame 14 and a second ordistal end 74 b that is opposed to proximal end 74 a along an axis 71.The body 74 includes a forward edge 75 a and a rearward edge 75 bopposed to the forward edge 75 a. The edges 75 a and 75 b extend atleast partially from the proximal end 74 a to the distal end 74 b. Thedistal end 74 b defines a distal-most contact surface 78, that can becurved, and is configured to engage the stop member 44 a to therebylimit the pivotal movement of the arm member 42 in the upward directionB1. As illustrated, when the rotatable member 70 is in lockingconfiguration, the distal surface 78 of the rotatable member 70 abutsthe upper engagement surface 44 u of the stop member 44 a, thuspreventing further upward rotational movement of the arm member 42.Contact surface 78 can be in contact with stop member 44 a whenrotatable body 74 is in the locked position and arm member 42 isoriented at its rest or first position in which angle α is zero.Alternatively when angle α is zero, arm limiter 60 and arm member 42 mayalso be configured to provide a clearance between contact surface 78 andstop member 44 a for ease of rotation of body 74 into and out of thelocked configuration, for manufacturing tolerances, and like factors. Inone embodiment, if arm member 42 has a different position from firstposition 40 a, the selected geometric configuration of at least one ofthe arm member 42, stop member 44, and rotatable member 70 can preventrotatable member 70 from transitioning into the second configuration.For example, if the arm member 42 is rotationally different from thefirst position 40 a (that is, angle α—illustrated in FIG. 4C—isnon-zero) by a predetermined amount as further discussed below, the edge75 a of the rotatable member abuts the rear surface 44 r which preventsthe rotatable member 70 from transitioning into the secondconfiguration.

Turning to FIGS. 3A and 3B, in accordance with the illustratedembodiment, the actuator 88 rotates member 70 between the openconfiguration and the locking configuration via movement of the transferlinkage 84 along the forward and rearward directions F and R. As shown,the transfer linkage 84 is an elongate rod or bar that includes arearward portion 85 r and a forward portion 85 f spaced from therearward portion 85 r in the forward direction F. The rearward portion85 r is coupled to the actuator 88 and the forward portion 85 f slideswithin an elongated slot 13 that is defined by a plate extending fromthe frame 14.

As shown in FIG. 3B, the biasing member 80 preferably is a strut thatincludes a rod 82 a and a biasing element 82 b, such as a coil spring,disposed about the rod 82 a between a moveable stop element 82 c and afixed stop element 82 d. The biasing member 80 defines a forward end 81f and a rearward end 81 r disposed rearwardly with respect to theforward end 81 f. As illustrated, opposed ends of the rod 82 a definethe forward and rearward ends 81 f and 81 r, respectively. The forwardend 81 f of the biasing member 80 is fixed to the rotatable member 70. Acoupling plate 83 connects the transfer linkage 84 to the rearward end81 r of the biasing member 80 at the fixed stop element 82 d. A distalend 83 e of the rod 82 a is slidable through a bore (not numbered)defined by the fixed stop element 82 d. As the transfer linkage 84 ismoved in the forward direction F by the actuator 88, the forward andrearward motion of the transfer linkage 84 is transferred to therotatable member 70. In particular, when the controller 92 receivesinput from the input device 8 to operate the wheelchair 10 in theelevated motion mode, the controller 92 attempts to put arm limiterassembly 60 in the locked configuration by actuating the actuator 88causing the transfer linkage 84 to move in the forward direction F andslide through the slot 13 along with the coupling plate 83. Movement ofthe coupling plate 83 urges the biasing member 80 toward the front ofwheelchair 10, which in turn causes the rotatable member 70 to pivotabout pivot axis P2 toward the second configuration (see FIG. 4A). Thespring 82 b is selected so that the force required to compress thespring 82 b is greater than the force required to urge the rotatablemember 70 into the second configuration uninhibited. Spring 82 b isconfigured to bias arm limiter assembly 60 toward the lockedconfiguration.

FIGS. 4A, 4B, 4C illustrate an arm limiter assembly 60 in the lockingconfiguration 71C (FIG. 4A), the open configuration 71O (FIG. 4B), and ablocked configuration 71B (FIG. 4C), whereby the arm member 42 ispreventing transition of the arm limiter assembly 60 from the openconfiguration 71O into the locking configuration 71C. Referring first toFIG. 4B, during normal operation and when the seat 22 is in the loweredposition, the arm limiter assembly 60 is in the open configuration. Theactuator 88 has been actuated to retract the transfer linkage 84 andthus move the rotatable member 70 into the open configuration. As notedabove, in the open configuration, the arm member 42 is rotatable throughits maximum range of rotation, such that the wheelchair 10 is operableto traverse an obstacle O or a descent along the surface G.

Turning to FIG. 4A, when wheelchair 10 is operated in an elevatedmode—when the seat 22 is in the raised position—the arm limiter assembly60 has transitioned into the locked configuration, with one exceptiondiscussed below. For instance, the actuator 88 cause the transferlinkage 84 to move along the forward direction F, which in turn causesthe rotatable member 70 to transition into the locking configuration asshown in FIG. 4A. Because the rotatable member 70 has pivoted intolocking configuration, the distal surface 78 of the rotatable memberabuts the upper engagement surface 44 u of the stop member 44 a, thuspreventing further upward rotational movement of the arm member 42.Accordingly, as the seat 22 is elevated into the raised position, theforward arm member 42 will have a limited range of rotation such thatthe wheelchair 10 is not operable to ascend an obstacle O along thesurface G. When seat 22 is moved into a lowered position, the armlimiter assembly 60 transitions back into the open configuration suchthat range of motion of the arm member 42 is restored. In someembodiments, the wheelchair 10 is configured to require operation in thestandard mode, when the seat 22 is lowered, before the full range ofmotion to the arm assembly 38 is restored and the obstacle can be safelytraversed.

Referring now to FIG. 4C, if front wheel 46 is on uneven ground surfaceG relative to the drive wheels 32, such as when the wheelchair beginstraversing the obstacle O, the forward extending arm member 42 ispivoted in an upward rotational direction B1 (that is, angle α ispositive) away from the first position 40 a toward the second position40 b. For example, the second position 40 b illustrated in FIG. 4C canbe when the arm member 42 is rotationally different from the firstposition 40 a by a predetermined angle. In some embodiments thepredetermined angle is by at least six (6) degrees, at least (5)degrees, at least four (4) degrees, at least three (3) degrees or atleast two (2) degrees. In other embodiments, the predetermined angle isat least about six (6) degrees, at least about five (5) degrees, atleast about four (4) degrees, at least about three (3) degrees or atleast about two (2) degrees. As illustrated, the angle α2 between thefirst line I1 and the fixed line I2 is about 4 degrees. If thecontroller 92 receives a request to operate the wheelchair in theelevated mode and elevate the seat 22 into the raised position (e.g., anelevated position that is pre-determined or selected to merit engagementof an anti-tip safety feature such as one or more of the featuresdescribed herein), the actuator 88 causes or attempts to cause thetransfer linkage 84 to move in forward direction F, which in turn causesor attempts to cause the rotatable member 70 to advance toward thelocking configuration. Because the arm member 42 is pivoted upwards, therear surface 44 r of the stop member 44 a abuts the forward edge 75 a ofthe rotatable member 70, preventing further rotation of the rotatablemember 70 into the locking configuration. However, even when the forwardextending arm member 42 is pivoted upwards away from the first position40 a into the second position 40 b, the actuator 88 causes the transferlinkage 84 to bias the rotatable member 70 toward the lockingconfiguration. More specifically, displacement of the transfer linkage84 and the coupling plate 83 causes the biasing element 82 b to compressas shown in FIG. 4C. The compressed spring 82 b applies a force to themoveable stop element 82 c urging the rotatable member 70 toward thelocked configuration, which as shown is abutting the stop 44 a. Oncewheelchair 10 has moved to a location on the surface G such that thefront wheel 46 and the drive wheels 32 are on flat, level ground (i.e.the first position 40 a), the compressed biasing element 82 b willautomatically urge the rotatable member 70 into the second configurationas shown in FIG. 4A.

The wheelchair 10 in some embodiments can further include a linkageassembly that operatively connects the lift mechanism 18 to the armlimiter assembly 60 such that as the seat 22 is moved from the loweredposition 5L to the raised position 5R, the linkage assemblyautomatically causes the arm limiter assembly 60 to move from the firstor open configuration toward the second or locked configuration. Thelinkage assembly (not illustrated) can be configured such that the linkcan be capable of connecting to the lift mechanism 18 only when thefront wheels 46 and the drive wheels 32 are on substantially evenground, for instance when the front wheels 46 are in the first position40A as described above with respect to FIG. 2A-4C. In an embodiment, thelinkage can include a hook member that is movable between an engagedposition whereby the hook member is capable of connecting to the liftmechanism 18 and a disengaged position hereby the hook member isincapable of connecting to the lift mechanism 18. It should beappreciated, however, that in such embodiments, the link can haveconfigurations other than the hook member as desired. For instance, thelinkage assembly may include one or more elongate legs secured to therotatable member 70, 170, a connection member that operatively connectsthe lift mechanism 18 to the one or more elongate legs, and one or moresprings connected to the one or more elongate legs and the rotatablemember which are configured to bias the rotatable member 70, 170 intothe second configuration. The connection member include a cable orassembly of rods or connection bars that engage the lift mechanism andselectively engage the one or more elongated legs. When the liftmechanism causes the seat 22 to move from the raised position into thelowered position, the linkage assembly may cause the rotatable member70, 170 to rotate from the locking configuration into the openconfiguration. Movement of the seat 22 from the lowered position to theraised position, permits the rotatable member 70, 170 to move from theopen configuration into the locking configuration.

Referring to FIG. 5, the wheelchair 10 includes control system 90 thatincludes a controller 92 configured to operate the wheelchair 10 indifferent operational modes (e.g., one or more of the operation modesdescribed herein). The controller 92 in some embodiments is inelectronic communication with the lift mechanism motor 20, the drivemotors 34 (or multiple drive motors if present), and the actuator oractuators 88. As noted above, the input device 8 is also in electroniccommunication with the controller 92. Further, a plurality of sensors 96a-96 c can include, for example, one or more position sensors 96 a thatcan determine the position of the components of the arm assembly 38 andarm limiter assembly 60, a seat-position sensor 96 b, and an inclinationsensor 96 c.

The controller 92 can be configured as a computing device configured toprocess input signals and control operation of the wheelchair 10. Thecontroller can include a processing portion 94 a, a memory portion 94 b,an input/output portion 94 c, and a user interface (UI) portion 94 d. Itis emphasized that the block diagram depiction of the computing devicecontrol system 90 is exemplary and not intended to imply a specificimplementation and/or configuration. The processing portion 94 a, amemory portion 94 b, an input/output portion 94 c, and a user interface(UI) portion 94 d can be coupled together to allow communicationstherebetween. As should be appreciated, any of the above components maybe distributed across one or more separate control boards as needed.

In various embodiments, the input/output portion 94 c includeselectronic connectors for wired connections to the lift motor 20, drivemotors 34, and actuators 88. The input/output portion 94 c is capable ofreceiving and/or sending signals information pertaining to operation ofthe lift mechanism, drive motors 34 and actuators 88. The input/outputportion is configured to receive information or signals from the inputdevice 8 or sensors 96 a-96 b. The signals can include inputs, such asinstructions to cause the actuator 88 to move the transfer linkage 84 inthe forward and rearward direction F and R, or data, such as theposition of the seat 22. Depending upon the exact configuration and typeof processor, the memory portion 94 b can be volatile (such as sometypes of RAM), non-volatile (such as ROM, flash memory, etc.), or acombination thereof. The controller 92 can include additional storage(e.g., removable storage and/or non-removable storage) including, butnot limited to, tape, flash memory, smart cards, CD-ROM, digitalversatile disks (DVD) or other optical storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,universal serial bus (USB) compatible memory, or any other medium whichcan be used to store information and which can be accessed by thecontroller 92. The user interface portion 94 d can include an inputdevice 8 and allows a user to communicate with the controller 92 andcontrol operation of wheelchair as further detailed below.

Each arm limiter assembly 60 can further include one or more positionssensors 96 a in communication with the controller 92. For example, eacharm limiter assembly 60 can include a first position sensor that isconfigured to detect when the rotatable member 70 is in the lockingconfiguration. In some embodiments, a second position sensor isconfigured to detect the position of the arm member 42. For instance,the arm position sensor can include a limit switch that detects when thearm member 42 is in the first position 40 a or the position sensor candetect the second position 40 b as well as any incremental positionsbetween the first and second positions 40 a and 40 b. Based on thedetected positions, the controller is configured to determine, based onthe detected positions of the arm member 42, if the arm member 42 islocked such that it is within the second, more limited range ofrotation. Furthermore, the position data can be used by the controller92 to cause the rotatable member 70 to progressively restrict the rangeof rotation of the forward arm member 42 relative to the frame 14.Preferably, controller 92 enables operation in the normal elevated modeonly when arm limiter 60 is in the locking configuration. The actuator88 can be configured to progressively move the rotatable member 70 basedon at least one of speed of the wheelchair 10, the distance the seat isspaced from the frame 14, and the position of the arm member 42 as thewheelchair moves down an obstacle.

The seat-lift sensor 96 b can be a limit switch that is configured todetect when the seat 22 has been moved out of the lowered position. Forexample, the seat-lift sensor detects when the seat 22 is in contactwith the frame 14. If the seat 22 is not in contact with the frame 14,the sensor 96 b can transmit a signal to the controller 92. In certainembodiments, the seat-lift sensor 96 b can be a limit switch that isconfigured to detect when seat is moved out the lowered position. Thecontroller 92 can cause a message to display on the input device 8 orcause some other operation as needed and based on inputs from the othersensors.

The inclination sensor 96 c is configured to detect whether the frame 14is in a level position with respect to a horizontal plane or an inclinedor unleveled position with respect to the horizontal plane alongforward-rearward direction F-R and along a lateral direction C that isperpendicular to the forward-rearward direction F-R. The lateraldirection C is not illustrated in the figures. The horizontal planeextends through the frame 14 is parallel to the surface G when thewheelchair 10 is on a flat, level ground surface G. In accordance withthe illustrated embodiment, the inclination sensors 96 c can be securedthe frame 14 and oriented roughly parallel to the surface G. Theinclination sensor 96 c can measure the angular position data of theframe 14 relative to horizontal along the forward-rearward direction F-Rand along the lateral direction C. The angular position data can be sentto the controller 92. The processing portion 94 determines, based on theangular position data, if the angular position of the frame 14 is withina predetermined threshold with respect to the horizontal plane in boththe forward-rearward direction F-R and lateral direction C. Thepredetermined threshold is the range of inclination that is slightenough such that operation of the wheelchair 10 in the elevated motionmode would not cause a significant risk of instability due to theelevated center of gravity. The predetermined threshold depends on theparticular parameters of the wheelchair and may be empirically chosen aswill be understood by persons familiar with wheelchair design. For theembodiment shown in the figures, the inclination threshold may be about1 degrees of inclination. If the frame 14 is inclined with respect tothe horizontal plane (the inclination exceeds the predeterminedthreshold) compared with its at-rest state, the controller 92 mayprevent operation of the wheelchair in the elevated motion mode or mayrestrict operation to an elevated-inhibited mode. For instance, if thecontroller 92 receives an input from the input device 8 to operate thewheelchair 10 in the elevated motion mode and the frame 14 is inclinedwith respect the horizontal plane, the controller 92 will only operatethe wheelchair 10 in an elevated motion mode if the arm limiterassemblies 60 are in the locking configuration. If, however, the frame14 is not inclined with respect to the horizontal plane (the inclinationis within the predetermined threshold) and the controller 92 receives aninput to operate in the elevated motion mode, the controller 92 causesthe lift mechanism to elevate the seat 22 to the raised position. Asdiscussed earlier, the arm limiter assembly 60 would be moved into thelocking configuration as well. In an embodiment, the inclination sensor96 c can include an accelerometer and/or gyroscope, or others as needed.

The input device 8 is in communication with the controller 92 andconfigured to be operated by the occupant of the wheelchair 10. Theinput device 8 can include a joystick, a keypad and a display. Thejoystick can cause the wheel chair to move forward, rearward, or turn tochange directions. The keypad includes input buttons that controloperation of the wheelchair 10. The display can cause the display ofnotifications regarding wheelchair operation. The keypad and display canbe integrated into a touch screen that receives user inputs and causethe display of various messages regarding wheelchair operation. Thedisplay or keypad and/or display can include input buttons that controlvarious operational aspects of the wheelchair. For instance, the keypadinclude buttons that when depressed cause the wheelchair 10 to operatein the elevated motion mode. The controller 92 is configured to, inresponse to inputs from the input device 8 to operate the wheelchair 10in the elevated motion mode, cause the input device 8 to display amessage or otherwise indicate that the elevated motion mode ispermitted. If the elevated motion mode is permitted, controller 92causes the lift mechanism to move the seat 22 into the raised positionwhen the frame 14 is level and the arm limiter assembly 60 is in thelocking configuration.

The wheelchair 10 is, in some embodiments, configured to operate in theelevated motion mode only when one or more safety criteria aresatisfied. As noted above, the safety criteria can include the positionof the seat 22 (e.g., raised from its lowermost position), inclinationof the frame 14, and the configuration of the arm limiter assemblies 60.If the seat 22 is in raised position, the center of gravity is elevatedwhich decreases wheelchair stability. Further, the risk of tipping thewheelchair 10 increases when wheelchair 10 is attempting to ascend anobstacle and the seat is elevated. Further, stability is adverselyaffected when the frame 14 is inclined. The arm limiter assemblies 60are configured to limit the ability of the wheelchair 10 to ascend anobstacle along the surface G if the seat is in raised position.Accordingly, if the controller 92 determines that fewer than all of thesafety criteria are met, the controller 92 causes the input device 8 todisplay a message or otherwise indicate that the elevated motion mode isnot permitted or is restricted to the elevated-inhibited mode.

An embodiment of the present disclosure includes methods for operatingwheelchair 10 in the standard mode, as shown in FIG. 6A, and theelevated motion modes, as shown in FIG. 6B. Turning to FIG. 6A, assumingthat wheelchair 10 is on flat, level ground and the seat is in the fullylowered position, a method according to an embodiment includes steps300-320. In step 300 the occupant of the wheelchair 10 can request tooperate the wheelchair 10 in the elevated motion mode via the inputdevice. At step 304, the controller in response to this input from theoccupant causes the arm limiter assemblies 60 to move toward the lockedconfiguration.

At step 308, the controller 92 receives angular position data frominclination sensor (e.g., inclination sensor 96 c). The controller 92will determine, based on the angular position data obtained from theinclination sensor, whether the frame 14 is level. At step 312, if theframe 14 is not level, the controller 92 causes an indication to displayon the display device that the elevated motion mode is not permitted.The controller 92 can also cause the display of message indicating thatthe occupant should drive the wheelchair 10 to level, flat ground. If,in step 308, the controller determines that the frame 14 is level,process control is transferred to step 316.

In step 316, the arm limiter position sensors (e.g., position sensors 96a) send a signal to the controller 92 regarding the arm limiter positiondata for the arm limiter assemblies 60. The controller 92 determines,based on the arm limiter position data, whether the arm limiterassemblies 60 are in the locked configuration. If the controller 92determines that the arm limiter assemblies 60 are not in the lockedconfiguration, the controller 92 causes an indication to display on thedisplay device that the elevated motion mode is not permitted. Thecontroller can also cause the display of message indicating that theoccupant should drive the wheelchair 10 to level, flat ground. At thisinstance, the arm member 42 may be in the second position 40 b such thatstop member 44 a inhibits rotation of the rotatable member 70 into thesecond configuration (see FIG. 4C). When the wheelchair 10 has moved tolevel, flat ground, the arm member 42 is moved back toward the firstposition and the biasing member 80 will automatically urge the armlimiter assembly 60 into the locked configuration as discussed above.

At step 320, the controller 92 determines, based on inputs from eachsensor, that all safety criteria are met. For instance, the controller92 determines if the seat 22 is in the lowered position and the armlimiter assembly 60 is in the locked configuration. The controller 92will indicate via the display device that operation of wheelchair 10 inthe elevated motion mode is permitted. Process control is transferred tostep 330 shown in FIG. 6B.

Turning now to FIG. 6B, a method for operating the wheelchair 10 in theelevated motion mode is illustrated. At step 330, controller 92 can,based on input from the input device 8 or automatically, cause the liftmechanism 18 to raise the seat 22 from the lowered position into theraised position. At step 334, the controller can cause the actuators 88to move the rotatable members 70 toward the locked configuration.

At step 338, the controller 92, based on inputs from the inclinationsensors (e.g., inclination sensor 96 c) and arm limiter position sensors(e.g., position sensors 96 a), can determine if the frame 14 is leveland if the rotatable members 70 are in the locked configuration. Inother words, in step 338, the controller 92 determines if all safetycriteria are met. At step 342, if all safety criteria are met, thewheelchair 10 is permitted to operate in the elevated motion mode andthe controller 92 powers the drive motors 34 such that the wheelchair 10is capable of moving within the maximum raised-seat drive speed (e.g., 0mph to 5 mph). In this regard, the controller 92 operates the drives upto the maximum raised-seat drive speed when the seat 22 is in the raisedposition and the rotatable member 70 is in the locked configuration. Atstep 342, if the controller 92 determines that less than all of thesafety criteria are met when the wheelchair 10 is in the elevated motionmode, the controller 92 powers the drive motors 34 such that thewheelchair is capable of moving within the maximum raised-inhibiteddrive speed range (e.g., 0 mph to 3.75 mph). In this regard, thecontroller 92 operates the drive motors 34 so as to advance thewheelchair 10 up to the maximum raised-inhibited seat drive speed whenthe seat 22 is in the raised position and the rotatable member 70 is inthe open or first configuration. As noted above, the upper limit of themaximum raised-inhibited seat drive speed range is less than the upperlimit of the maximum raised-seat drive speed range. Accordingly, thewheelchair 10 is configured to limit the maximum attainable speed whenthe rotatable members 70 are in the open configuration and the armmembers 42 are pivotable so as to traverse an obstacle.

At step 346, if the controller determines that all of safety criteriaare not met, the controller 92 causes the display device to display amessage to the occupant that the elevated motion mode is not permitted.The controller 92 can also cause the display of message indicating thatthe occupant should drive the wheelchair 10 to level, flat ground. Ifduring operation of wheelchair 10 in the elevated motion mode thewheelchair 10 traverses an inclined surface or some other obstacle, theinclination sensor obtains the angular position data for the frame 14 asdiscussed above. At step 348, if the controller 92 determines, based onangular position data, that the frame 14 has transitioned from a levelposition to an inclined position that exceeds the predeterminedthreshold, the controller 92 automatically causes the drive motors 34 toreduce the speed of the wheelchair 10 to within the maximumraised-inhibited drive speed range.

Accordingly, in response to input from an input device to operate thewheelchair in an elevated motion mode and in response to data obtainedfrom the inclination sensors and arm limiter position sensors, thecontroller 92 according to some embodiments is configured to: (i) powerthe drive motors 34 such that the wheelchair is capable of moving withinthe maximum raised-seat drive speed range when the seat is in the raisedposition, the locking mechanism is in the locked configuration, and theframe 14 is level. Further, the controller is configured to power thedrive motors 34 such that the wheelchair 10 is capable of moving at themaximum raised-inhibited drive speed when the seat 22 is in the raisedposition and either A) the rotatable member is in the openconfiguration, and/or B) the frame is in the unleveled position. Itshould be appreciated, however, that the controller can be configured tooperate the wheelchair 10 in an desired mode based on data obtained fromthe sensors in any order desired and after any desired criteria are met.

FIGS. 7-13B illustrate wheelchairs according to alternate embodiments ofthe present disclosure. Turning to FIGS. 9A and 9B, a powered wheelchair 110 is configured similar to the powered wheelchair 10 describedabove and illustrated in FIGS. 1-5. Accordingly, the description belowregarding wheelchair 110 will use similar reference signs to identifyelements common to wheel chair 10 and wheelchair 110. Powered wheelchair110 includes a frame 14, drive wheels 32 coupled to the frame 14,forward arm assemblies 38, rear arm assemblies 48, a lift mechanism 18and a seat 22 supported by the lift mechanism 18. Further, the poweredwheel chair 110 includes control system 90 and associated sensors 96 a,96 b, 96 c.

Continuing with FIGS. 9A and 9B, in the alternative embodiment, thepowered wheel chair 110 includes a pair of arm limiter assemblies 160.Only one arm limiter assembly will be described below, as the oppositearm limiter assembly in the pair is similarly constructed. The armlimiter assembly 160 includes a rotatable member 170 pivotably coupledto the frame 14, a compressible or moveable end 174 b, an actuator 88(not shown in FIGS. 9A and 9B), a linkage 84 coupled to the actuator,and a biasing member 80 coupled to the linkage 84 and the rotatablemember 170. Actuation of the actuator 88 translates the linkage 84,which in turn, causes the biasing member 80 to advance the rotatablemember 70 from the open configuration 71O (FIG. 9A) into the lockedconfiguration 71C (FIG. 9A).

At least a portion of the rotatable member 170 is configured to at leastpartially compress along an axis 71 in response to upward movements ofthe arm member 42 against the end 174 b when the rotatable member 70 isin the locking configuration, as further detailed below. The biasingmember 80 can be directly or indirectly coupled to the linkage 84 andthe rotatable member 170

Referring to FIGS. 7 and 9B, the rotatable member 170 includes a body173 b, a translating member 176 moveably coupled to the body 173 b, anda biasing member 178. As shown in FIG. 9B, when the rotatable member 170is in the locking configuration 70L and the wheelchair 10 ascends overan obstacle O, the biasing member 178 allows the arm member 42 topartially rotate upwards against the force of biasing member 178 so asto prevent the wheelchair from high-centering (e.g. drive wheels areable to contact the ground when the chair ascends a low obstacle).Continuing with FIG. 7, the rotatable member 170 has a first or proximalportion 170 a and a second or distal portion 170 b spaced from theproximal portion 170 a along the axis 71 in a distal direction 4. Thedistal direction 4 is aligned with and parallel to the axis 71. Theproximal portion 170 a includes a proximal end 174 a and the distalportion 170 b includes the moveable or distal end 174 b. As illustrated,the translating member 176 defines the moveable end 174 b. The biasingmember 178 is disposed at least partially between the proximal portion170 a and the distal portion 170 b. The biasing member 178 isillustrated as a spring 170 c. And while a helical compression spring isillustrated, other spring types could be used as well. Further, thebiasing member 170 c can have other configurations, such as for example,a hydraulic piston as desired, a compressible material, such as gel orfoam, or other device or structure than provide a counter force againstforce applied to translating member 176 to cause the translating memberto advance along axis 71.

Continuing with FIG. 7, the body 173 b is configured to couple to theframe 14 and support the translating member 176 and biasing member 178.The body 173 b defines the proximal end 174 a, a forward side 175 a, arearward side 175 b opposed to the forward side 175 a along a transversedirection 6 that is perpendicular to the axis 71. The body 173 b definesa width W1 (not shown) that extends from the forward side 175 a to the arearward side 175 b in the transverse direction 6. The body 173 bincludes a pair of arms 173 e and 173 f defining a gap (not numbered).The body 173 defines a surface 173 s that extends from arm 173 e to arm173 f along the transverse direction 6, and a channel 171 a extends fromthe surface 173 s into the body 173 b along the axis 71 toward theproximal end 174 a. An elongate slot 173 d extends through the body 173b and is in communication with the channel 171 a. The body 173 b can bea rigid plate or rod. As illustrated, the body 173 b is an elongateplate with extending arms 173 e and 173 f.

As noted above and illustrated in FIG. 7, the translating member 176 isconfigured to compress or move in response to force applied to it by thearm member 42. More specifically, in accordance with the illustratedembodiment, the translating member is translatable 1) toward the body173 b in an upward or proximal direction 2 that is opposite to distaldirection 4, and 2) away from the body 173 b in the distal direction 4.The translating member 176 includes a connection member 171 b, such as arod, that is moveably coupled to the body 173 b with a fastener 171 c.The rod 171 b is received by the channel 171 a and moveable within thechannel 171 a along the axis 71. The fastener 171 c extends through theslot 173 d and is fixed to the portion of the rod 171 b in the channel171 c. As the rod 171 b moves within the channel 171 a, the fastenerslides within the slot 173 b. It should be appreciated, however, thatthe translating member 176 and the body 173 b can be coupled together inother ways. For example, the proximal portion 170 a can include the rodand the distal portion 170 b can define the channel as desired. Further,the connection member 171 b is not limited to a rod but can be a plateor other elongate structure.

Continuing with FIG. 7, the distal end 174 b, such as the translatingmember 176, can define an outer surface with any shape or profile thatis configured to engage the arm member 42 as the arm member 42 pivotsrelative to the frame 14 during operation of the wheelchair.Accordingly, the distal end 174 b can have a surface that is configuredto abut the arm member 42 only when the rotatable member 70 or the armmember 42 is in specific orientations relative to the frame 14, e.g.when the rotatable member 70 is the locking configuration. In addition,the distal end 174 b can be configured to progressively restrictrotational movement of the arm member 42 dependent upon the orientationof the rotatable member 70 relative to the frame 14. For instance, therotational limit the rotatable member 70 applies to the arm member 42can vary as the position of the rotatable member 70 varies with respectto the frame 14.

In accordance with the embodiment illustrated in FIG. 7, the translatingmember 176 further defines an outer surface 179 a that is configured toengage the stop member 44 a of the arm member 42. For instance, theouter surface 179 a includes a forward surface portion 179 f, a rearwardsurface portion 179 r opposite to the forward surface portion along atransverse direction 6, and a distal-most surface portion 179 d thatextends from the forward surface portion 179 f to the rearward surfaceportion 179 r. The forward surface portion 179 f is configured to engagethe rear surface 44 r of the arm assembly 42 if the arm member 42 isascending an obstacle before the rotatable member 170 has transitionedinto the locking configuration (see e.g. FIG. 4C). And while the forwardand rearward surface portions 179 f and 179 r are illustrated parallelto the axis 71, the forward and rearward surface portions 179 f and 179r can have any shape, curvature, or inclination as needed. Thedistal-most surface portion 179 d, or distal surface 179 d, isconfigured to abut the upper surface 44 u of the stop member 44 a whenthe rotatable member 170 is in the locking configuration. Thetranslating member 176 defines a width W1 (not shown) that extends fromthe forward surface portion 179 f to the rearward surface portion 179 rin the transverse direction 6. The body 173 b defines a width W2 (notshown) that extends from the forward side 175 a to the rearward side 175b in the transverse direction 6. As illustrated the width W1 of thetranslating member 176 is about equal to the width W2 of the body 173 b.However, it should be appreciated that the width W1 of the translatingmember 176 can be greater than the width W2 of the body 173 b. Forexample, in embodiments where the translating member 176 is configuredfor progressive restriction of rotational motion of the arm member 42,the translating member width W1 could be greater than the width W2 ofthe body 173 b.

FIGS. 8A-8D schematically illustrate various alternate embodiments ofthe translating member 176. As noted above, the translating member candefine any particular shape and/or surface profile to engage the armmember 42 during operation of the wheelchair. For instance, thetranslating member 192 a (FIG. 8A) defines first and second distalsurfaces 199 a and 198 a. The first surface 199 a is inclined at anoblique angle with respect to the axis 71 and the transverse direction6, the second surface 198 a is normal to the axis 71. Translating member192 b (FIG. 8B) defines a distal surface 198 b that is slightly curvedwith respect to the axis 71 and is inclined along the transversedirection 6. Translating member 192 c (FIG. 8C) defines a distal surface198 c that is curved with respect to the axis 71 and the surface extendsfrom the intersection of the axis 71 and surface 198 c toward edges 175a and 175 b. The leading surfaces 192 a, 192 b, and 192 c provide a rampor cam surface for engaging stop member 44 a. Translating member 192 dshown in FIG. 8D defines a distal surface 198 d that inclines toward therearward side 175 b of the rotatable member 170.

Turning to FIGS. 10A-10D, a powered wheelchair 210 according to analternative embodiment of the present disclosure is configured similarto the powered wheelchair 10,110 described above and illustrated inFIGS. 1-5 and 9A-9B. For instance, the powered wheelchair 210 includes aframe 14, drive wheels 32 coupled to the frame 14, a pair of forward armassemblies 38, a pair of rear arm assemblies 48, and a lift mechanism 18mounted to the frame 14 and configured to move the seat 22 between thelowered and raised positions 5R. The powered wheelchair 210 includescontrol system 90 and sensors 96 a, 96 b, 96 c similar to the wheelchair10 described above. Accordingly, the description below regardingwheelchair 210 will use similar reference signs to identify elementscommon to wheelchair 10 and wheelchair 210.

In accordance with the alternative embodiment, the powered wheelchair210 includes a pair of arm limiter assemblies 260 configured toselectively engage the forward arm assemblies 38 so as to inhibitrelative motion between the arm assemblies 38 and frame 14 in certaininstances during operation of the wheelchair 210. As illustrated inFIGS. 10A-10C, the arm limiter assembly 260 includes a first matingmember 264 supported by the arm assembly 38 and a second mating member268 supported by the frame 14 that is configured to mate with the firstmating member 264 only when the front wheel 46 and drive wheel 32 are onsubstantially flat, level ground, for instance when the arm member 42 isin the first position 40 a (FIG. 10A, (similar to FIG. 3A).

Further, the arm limiter assembly 260 has a first or open configurationand a second or locked configuration. When the arm limiter assembly 160is in the open configuration as shown in FIGS. 10B and 10C, the firstand second mating members are not engaged and the arm assembly 38 canpivot through the first range of rotation. When the arm limiter assembly260 is in the second or locked configuration as shown in FIG. 10A, thefirst and second mating members are engaged with each other and the armassembly 38 is permitted to pivot through the second range of rotationthat is less than the first range of rotation. In the lockedconfiguration, the arm assembly 38 may still pivot to a limited extent,such as 4 degrees away from the first position 40 a, because the matingmember may be a slotted opening as explained more fully below.Alternatively, when the arm assembly 38 is in locked configuration, thearm assembly 38 may not pivot at all away from the first position 40 a.In the illustrated embodiment, the first mating member 264 can be anaperture 272 and the second mating member 268 can be a pin 276 that isconfigured to be received by the aperture 272. It should be appreciated,however, that the pin 276 can be supported by the arm assembly 38 andthe aperture 272 supported by the frame 14 as desired.

Continuing with FIGS. 10A-10D, the arm limiter assembly 260 includes anactuator 88, a linkage 284, and a pin assembly 286 coupled to linkage284. The pin assembly 286 includes a projection in the form a pin 276.In the illustrated embodiment, the pin 276 is the first mating member264. The arm limiter assembly 260 further includes a leg 274 fixed tothe arm member 42 and a plate 290 directly or indirectly coupled to theleg 274. The actuator 88 is in the position to maintain the pin 276 in aretracted position when the seat 22 is in the lowered position as shownin FIG. 10B to enable standard mode operation of the wheelchair. Theactuator 88 moves the pin 276 toward an engaged position whereby the pin276 is received by the aperture 272 when the controller 92 receives aninput to move the wheelchair 210 in the elevated motion mode and theseat 22 is in raised position as shown in FIG. 10A, or otherwise to lockthe front arm assembly 38.

The leg 274 is coupled to the arm member 42 proximate the pivot axis P1.As the arm member 42 rotates about the pivot axis P1, the leg 274 andthe plate 290 rotates about pivot axis P1. If the arm member 42 rotatesin a first rotation direction B1, the plate 290 rotates in the secondrotational direction B2 (FIG. 10B). The plate 290 includes a plate body292, a first surface 293, a second surface 294 opposed to the firstsurface 293, and a thickness T (not shown) that extends from the firstsurface 293 to the second surface 294. The plate can define an upperedge 295 and a lower edge 296. The plate is curved as it extends fromthe upper edge 295 to the lower edge 296. In addition, the plate 290defines at least one aperture 272 (FIG. 10D) that extends along adirection aligned or parallel to the thickness T. The aperture 272 issized and configured to receive the pin 276. More specifically, theplate 290 defines an aperture edge 275. The aperture edge 275 definesthe aperture 272. For instance, the aperture 272 can be an elongate slotelongate along a direction that is angularly offset with respect to thethickness either vertically with respect to forward-rearward direction.In other embodiments, the aperture can be circular, oval, or othershaped opening. Further, in alternative embodiments, the plate 290 isconfigured so that the pin 276 can ride along its surface until pin 276extends beyond an edge of the plate 290, such as the aperture edge 275or the lower edge in accordance with certain embodiments.

Continuing with FIGS. 10A-10D, in operation, controller 92 receives aninput to operate wheelchair 210 with the seat 22 in the raised position.In response, the controller 92 the causes the actuator 88 move the pin276 to move into an extended configuration toward the plate 290. Asshown in FIG. 10A, when the plate 290 is in an aligned position wherebythe aperture 272 is aligned with the pin 276, for example due toorientation of the arm member 42 along along flat, level ground G, thepin 276 extends into the aperture 272. When the pin 276 extends alongthe edge 275 into the aperture 272, the arm limiter assembly 260 is inthe locked configuration and movement of the arm member 42 is limited.If, however, the wheelchair 210 is traversing an obstacle O as shown inFIG. 10C and the seat 22 is in the lowered position, the arm member 42is pivoted upwards in a first rotational direction B1 and the plate 290moves downward toward the surface G. This in turn causes the plate 290to slide along the pin 276 such that the pin 276 is disposed adjacentthe surface 294 and positioned upward with respect to aperture edge 275.The plate 290 in this position blocks the pin 276 from extending intothe engaged position. Because the pin 276 is prevented from moving intothe engaged position in the aperture 272, the arm limiter assembly 260is prevented from transitioning into the second or locked configuration.The wheelchair 210 operates similar in some respects as to how thewheelchair 10, 110 operates when the arm limiter assembly 60, 160 isprevented from the transitioning to the locked configuration. Forinstance, the controller 92 may prevent operation of one or more aspectsof the wheelchair 210 in the elevated motion mode, for example, if thecondition of the arm limiter being in the locking condition is not met.After the wheelchair 210 traverses the obstacle O, the arm member 42pivots downwardly until the front wheel 46 and the drive wheels 32 areon flat, level ground as shown in FIGS. 10A and 10B. At this point, theplate 290 is moved upwardly sliding along the pin 276 until the pin 276is aligned with the aperture 272. The pin 276, via the actuator as notedabove, urges the pin 276 to extend along the aperture edge 275 into theaperture 272 placing the arm limiter assembly 260 in the lockedconfiguration. In this regard, the plate 290 is configured as a slidingmember.

The aperture 272 can be elongate along the direction the pin 276 slidesalong the plate 290. In such embodiments, the arm member 42 can pivotthrough the second range of rotation (less than the first range ofrotation) when the arm limiter assembly 260 is in the lockedconfiguration while pin 276 is located in slotted aperture 272. In thisregard, the plate 290 is configured to permit the arm member 42 to pivotup to 4 or 5 degrees away from the its initial position 40 a even whenthe arm limiter 260 is in the locked configuration. This particularembodiment permits the arm assembly 38 to traverse slight obstacles andprevent the arm assembly 38 and the arm limiter assembly 260 fromlocking out, and permits arm assembly 38 to be limited in its downward(direction B2) movement. It should be appreciated, however, that theaperture 272 can have a diameter or other dimension that issubstantially equal to that of the pin 276 such that when the pin 276 isreceived by the aperture 272, the forward extending arm 42 is fixedrelative to the frame 14 with little or no movement.

As illustrated, the aperture 272 is disposed between the upper and lowerplate edges 295 and 296 such that the pin 276 can extend along theaperture edge 275. It should be appreciated, however, that plate 290 canbe configured without an aperture that receives the pint 276. Forinstance, the lower edge 296 can define a surface along which the pin276 extends along in order to transition the arm limiter assembly 260into the second configuration. In other words, the plate 290 can bemoved into the locked or an aligned position when pin 276 is moveablealong the lower edge 296 into its engaged position.

Turning to FIGS. 11A and 11B another embodiment of wheelchair 310 isschematically illustrated including an arm limiter assembly 360according to yet another alternate embodiment of present disclosure. Thepowered wheelchair 310 according to an alternative embodiment of thepresent disclosure is configured similar to the powered wheelchair 10described above. Accordingly, the description below regarding wheelchair310 will use similar reference signs to identify elements common towheelchair 10 and wheelchair 310, such as the frame 14, drive wheels 32(not shown), forward arm assemblies 38, rear arm assemblies 48 (notshown), lift mechanism 18 (not shown), seat 22, and control system 90and sensors.

Continuing with FIGS. 11A and 11B, the arm limiter assembly 360 can beused on any one of the wheelchairs 10, 110, or 210 described above.Further, the wheelchair incorporating arm limiter assembly 360 mayinclude similar components and operation characteristics described aboveexcept as noted otherwise. The arm limiter assembly 360 includes a disc362 or a segment of a disc that is supported by the frame 14 andoperatively engaged with arm assembly 38, and in particular to theproximal end 43 p of the arm member 42. The arm limiter assembly 260includes a caliper or clamp 370 that is supported by the frame 14 of thewheelchair 310 (frame and wheelchair not shown in FIGS. 11A and 11B).The clamp 370 can have a pair of moveable pads 372 a and 372 b spacedapart with respect to each other to define a gap 373. The gap 373 issized to receive a portion of the disc 362 therein such there is nocontact or light contact between the pads 372 a and 372 b and thecorresponding surfaces of disk 362. The clamp 370 is configured toselectively engage the disc 362 to thereby restrict movement of the disc362 and the arm member 42. For instance, the clamp 370 can be coupled tothe actuator 88 such that when the actuator 88 is activated, themoveable arms 372 a, 372 b move toward each other in directions 385 aand 385 b against opposite surfaces 364 and 366 of the disc 362. In afirst or open configuration, the disc 362 is moveable in the gap 373 andthe arm member 42 is moveable through the first range of rotation ormotion. When the wheelchair 310 operates in an elevated motion mode, theactuator 88 closes the clamp 370 tightening against the disc 362.Because the disc 362 is thus fixed to the arm member 42, movement of thearm member 42 is stopped. In an alternative embodiment, the disc 326 canhave a protrusion or stop 368 that is positioned to align between theclamp arms 372 a, 372 b in the gap 373 when the arm member 42 isrotationally different from the first position 40 a by more than 4 or 5degrees. In this position, the disc 362, via the stop 368 in the gap373, prevent the clamp arms 372 a, 372 b from transitioning into theclamped configuration against the surface 364 and 366, which in turnprevents arm limiter assembly 360 from locking movement of the disc andarm member 42.

Turning to FIGS. 12A-12C, a wheelchair 410 is illustrated including anarm limiter assembly 460 according to yet another alternate embodiment.The powered wheelchair 410 is configured similar to the poweredwheelchair 10 described above and illustrated in FIGS. 1-5. Accordingly,the description below regarding wheelchair 410 will use similarreference signs to identify elements common to wheelchair 10 andwheelchair 410, such as the frame 14, drive wheels 32 (not shown),forward arm assemblies 38, rear arm assemblies 48 (not shown), liftmechanism 18 (not shown), seat 22, and control system 90 and sensors. Inthe alternative embodiment, the arm limiter assembly 460 can beconfigured as rear-ward arm limiter assembly.

FIGS. 12A, 12B, 12C schematically illustrate the arm limiter assembly460 in the locking configuration 71C (FIG. 12A), the open configuration71O (FIG. 12B), and a blocked configuration 71B (FIG. 12C), whereby thearm member 42 is preventing transition of the arm limiter assembly 460from the open configuration 71O into the locking configuration 71C. Inthe illustrated embodiment, the arm limiter assembly 460 can beconfigured as rearward arm limiter assembly. The arm limiter assembly460 includes an actuatable unit 462 coupled between the frame 14 and thearm member 42. The actuatable unit 462 can have a housing 464 and anelongate member 466 in the form of a rod or bar that extends out fromthe housing 464 and is movable with respect to the housing 464. FIG. 12Bshows the elongate member 466 in its retracted position. The extendedposition of elongate member 466 is shown in dashed lines in FIG. 12B.The elongate member 466 defines an end 468 spaced from the housing 464along a direction 469 that is aligned with and parallel to the forwarddirection F of the wheelchair 410. The arm limiter assembly 460 has 1) afirst or open configuration, whereby the elongate member 466 isretracted partially into the housing 464 such that the arm member 42 ispivotable through the first range of rotation as discussed above, 2) asecond or locked configuration where the elongate member 466 abuts thestop 44 a of the arm member 42, thereby preventing the arm member 42from pivoting upwardly with respect to the frame 14, and 3) a blockedconfiguration where the arm limiter assembly is prevented fromtransitioning into the locked configuration. The actuatable unit 462 canbe a hydraulic strut, magnetorhealogical strut, gas strut, or otherdevice configured to allow one component to move relative to anothercomponent to selectively engage the arm member 42 as described herein.

Referring first to FIG. 12B, during normal operation and when the seat22 is in the lowered position, the arm limiter assembly 460 is in theopen configuration. The actuator 88 has been actuated to cause theelongate member 466 to retract into the open configuration. Turning toFIG. 12A, when wheelchair 10 is operated in an elevated mode—when theseat 22 is in the raised position—the arm limiter assembly 460transitions into locked configuration such that elongate member 466 isextended to block upward movement of the arm member 42. Accordingly, asthe seat 22 is elevated into the raised position, the forward arm member42 will have a limited range of rotation such that the wheelchair 410 isnot operable to ascend an obstacle O along the surface G. Referring nowto FIG. 12C, if front wheel 46 is on uneven ground surface G relative tothe drive wheels 32, such as when the wheelchair 410 begins ascent ofthe obstacle O, the arm member 42 is pivoted in an upward rotationaldirection B1 away from the first position 40 a into the second position40 b that is rotationally different than the first position 40 a.Because the arm member 42 is pivoted upwards, the stop member 44 a abutsthe forward end 468 of the elongate member 466, preventing furtherprogression of the elongate member 466 into the locking configuration.Once wheelchair 410 has moved to a location on the surface G such thatthe front wheel 46 and the drive wheels 32 are on flat, level ground(i.e. the first position 40 a), the actuatable unit 462 is configured toautomatically urge the elongate member 466 into the lockingconfiguration as shown in FIG. 12A.

Turning to FIGS. 13A and 13B, a powered wheelchair 510 according to analternative embodiment of the present disclosure is configured similarto the powered wheelchair 10 described above and illustrated in FIGS.1-5. Accordingly, the description below regarding wheelchair 510 willuse similar reference numerals to identify elements common to wheelchair10 and wheelchair 510, such as the frame 14, drive wheels 32 (notshown), lift mechanism 18 (not shown), seat 22, and control system 90and sensors. The forward arm assemblies 38 are as described above exceptfor the stop member. In the alternate embodiment, the powered wheelchair510 includes a pair of rearward arm assemblies 548 configured to pivotrelative to the frame 14 between a first position 540 a when thewheelchair is operating on flat, level ground, and any number ofdifferent positions depending on if the wheelchair 510 is ascending anobstacle or initiating a decent down an incline. The rearward armassembly 548 is configured similar to the forward arm assembly 38describe above with reference to FIGS. 1-5 and this paragraph, andincludes an arm member 542, a rear wheel 47 coupled to the arm member542. The arm member 542 can include a stop member 544 a located in thesame place on the arm member 542 as stop member 44 a in poweredwheelchair 10. The stop member 544 a of the arm member 542 in theembodiment shown in FIGS. 13A and 13B is not rounded, but has a verticalcontact face and a horizontal top surface. The rearward arm assembly 548can move in a first rotational direction B1, e.g., upward, when thewheelchair 510 encounters an ascent, or a second rotational directionB1, e.g., downward, when the wheelchair 510 descends down an inclinedsurface.

The powered wheelchair 510 can be configured to limit relative movementof the rearward arm assembly 548 depending on the surface G thewheelchair 510 is operating along. For instance, the arm limiterassembly 560 has an open or first configuration in which the rearwardarm assembly 548 is moveable relative to frame 14 through a first rangeof rotation relative to the pivot axis P1, and a second or lockedconfiguration in which the rearward arm assembly 548 is prevented frommoving relative to the frame 14 as needed. For instance, in the lockedconfiguration, the arm limiter assembly 560 limits movement of the armassembly 546 through a second range of rotation that is less than thefirst range of rotation. It should be appreciated that the second rangeof rotation can include the rearward arm assembly 548 being rotationallyfixed relative to the frame 14. In the with the illustrated embodiment,the arm limiter assembly 560 shown in FIGS. 13A and 13B is configuredsimilar to the actuatable unit type arm limiter assembly 460 describedabove with reference to FIGS. 12A-12C. For example, the arm limiterassembly 560 includes an actuatable unit 562 coupled between the frame14 and the arm member 42. The actuatable unit 562 can have a housing 564and an elongate member 566 in the form of a rod or bar that extends outfrom the housing 564 and is movable with respect to the housing 564.FIG. 13B shows the elongate member 566 in its retracted position. Itshould be appreciated that wheelchair 510 can include anyone of the armlimiter assemblies 60, 160, 260, and 360 as described above, or any armlimiter assembly described further below.

Turning to FIGS. 16A and 16B, an alternative embodiments of a poweredwheelchair 610, the arm assembly 638 can be configured such that thewheel 46 or wheel axis A1 is translatable from the first position 40 ato the second position 40 b. In the embodiment shown in FIGS. 16A and16B, powered wheelchair 610 is configured similar to the poweredwheelchair 10 described above and illustrated in FIGS. 1-5. Accordingly,the description below regarding wheelchair 610 will use similarreference numerals to identify elements common to wheelchair 10 andwheelchair 610, such as the frame 14, drive wheels 32 (not shown), liftmechanism 18 (not shown), seat 22, arm limiter assembly 60, controlsystem 90 and sensors. In and alternate embodiment, the poweredwheelchair 610 includes a pair of forward arm assemblies 638 moveablycoupled to a track 650 that extends forwardly from the frame 14. Thetrack 650 receives the proximal end 43 p (shown in dashed lines in FIGS.16A and 16B) of the arm member 42. As illustrated, the proximal end 43 pis slidable within the track 650 via a bearing or roller mechanism (notshown) so that arm member 42 and wheel 46 are translatable along thetrack 650 upwardly or downwardly relative to the frame 14 in a lineardirection C. The linear direction C can extend along the verticaldirection V or may be angularly offset (as illustrated) with respect thevertical direction V. Accordingly, the arm assemblies 638 are coupled tothe frame 14 such that the wheel 46 is translatable from between thefirst position 40 a and the second position 40 a depending on theobstacle the wheel 46 is traversing. As noted above, operation of thearm assembly 638 is similar to operation of the arm assembly as the 008patent noted above. The disclosure of the 008 patent is incorporated byreference herein for all purposes.

Continuing with FIGS. 16A and 16B, in alternative embodiments when thearm limiter assembly 60 is in the disengaged or open configuration thearm member 42 is translatable from the first position 40 a through afirst range of motion. When the arm limiter assembly 60 is in theengaged or locked configuration, the arm member 42 is translatablethrough a second range of motion that is less than the first range ofmotion. While arm member 42 is translatable along the linear directionC, the positional difference of the wheel 46 in the first and secondpositions 40 a and 40 b can have an angular component. The firstposition 40 a in FIG. 16A can be defined by first reference and secondlines (not shown) that intersect the front wheel axis A1 and aforward-most point (651) located on the bottom 14 b of the frame 14.When the arm assembly 638 translates the wheel 46 from the firstposition 40 a to the second position 40 b, the second reference linedefines an angle α1 (not shown) with the first reference line (notshown). Accordingly, the range of motion as described with respect towheelchair 16 can correspond to range of rotation described with respectto the wheelchair 10.

FIGS. 8A-8D schematically illustrate various alternate embodiments ofthe translating member 176. As noted above, the translating member candefine any particular shape and/or surface profile to engage the armmember 42 during operation of the wheelchair. For instance, thetranslating member 192 a (FIG. 8A) defines first and second distalsurfaces 199 a and 198 a. The first surface 199 a is inclined at anoblique angle with respect to the axis 71 and the transverse direction6, the second surface 198 a is normal to the axis 71. Translating member192 b (FIG. 8B) defines a distal surface 198 b that is slightly curvedwith respect to the axis 71 and is inclined along the transversedirection 6. Translating member 192 c (FIG. 8C) defines a distal surface198 c that is curved with respect to the axis 71 and the surface extendsfrom the intersection of the axis 71 and surface 198 c toward edges 175a and 175 b. The leading surfaces 192 a, 192 b, and 192 c provide a rampor cam surface for engaging stop member 44 a. Translating member 192 dshown in FIG. 8D defines a distal surface 198 d that inclines toward therearward side 175 b of the rotatable member 170.

Turning to FIGS. 10A-10D, a powered wheelchair 210 according to analternative embodiment of the present disclosure is configured similarto the powered wheelchair 10,110 described above and illustrated inFIGS. 1-5 and 9A-9B. For instance, the powered wheelchair 210 includes aframe 14, drive wheels 32 coupled to the frame 14, a pair of forward armassemblies 38, a pair of rear arm assemblies 48, and a lift mechanism 18mounted to the frame 14 and configured to move the seat 22 between thelowered and raised positions 5R. The powered wheelchair 210 includescontrol system 90 and sensors 96 a, 96 b, 96 c similar to the wheelchair10 described above. Accordingly, the description below regardingwheelchair 210 will use similar reference signs to identify elementscommon to wheelchair 10 and wheelchair 210.

In accordance with the alternative embodiment, the powered wheelchair210 includes a pair of arm limiter assemblies 260 configured toselectively engage the forward arm assemblies 38 so as to inhibitrelative motion between the arm assemblies 38 and frame 14 in certaininstances during operation of the wheelchair 210. As illustrated inFIGS. 10A-10C, the arm limiter assembly 260 includes a first matingmember 264 supported by the arm assembly 38 and a second mating member268 supported by the frame 14 that is configured to mate with the firstmating member 264 only when the front wheel 46 and drive wheel 32 are onsubstantially flat, level ground, for instance when the arm member 42 isin the first position 40 a (FIG. 10A, (similar to FIG. 3A).

Further, the arm limiter assembly 260 has a first or open configurationand a second or locked configuration. When the arm limiter assembly 160is in the open configuration as shown in FIGS. 10B and 10C, the firstand second mating members are not engaged and the arm assembly 38 canpivot through the first range of rotation. When the arm limiter assembly260 is in the second or locked configuration as shown in FIG. 10A, thefirst and second mating members are engaged with each other and the armassembly 38 is permitted to pivot through the second range of rotationthat is less than the first range of rotation. In the lockedconfiguration, the arm assembly 38 may still pivot to a limited extent,such as 4 degrees away from the first position 40 a, because the matingmember may be a slotted opening as explained more fully below.Alternatively, when the arm assembly 38 is in locked configuration, thearm assembly 38 may not pivot at all away from the first position 40 a.In the illustrated embodiment, the first mating member 264 can be anaperture 272 and the second mating member 268 can be a pin 276 that isconfigured to be received by the aperture 272. It should be appreciated,however, that the pin 276 can be supported by the arm assembly 38 andthe aperture 272 supported by the frame 14 as desired.

Continuing with FIGS. 10A-10D, the arm limiter assembly 260 includes anactuator 88, a linkage 284, and a pin assembly 286 coupled to linkage284. The pin assembly 286 includes a projection in the form a pin 276.In the illustrated embodiment, the pin 276 is the first mating member264. The arm limiter assembly 260 further includes a leg 274 fixed tothe arm member 42 and a plate 290 directly or indirectly coupled to theleg 274. The actuator 88 is in the position to maintain the pin 276 in aretracted position when the seat 22 is in the lowered position as shownin FIG. 10B to enable standard mode operation of the wheelchair. Theactuator 88 moves the pin 276 toward an engaged position whereby the pin276 is received by the aperture 272 when the controller 92 receives aninput to move the wheelchair 210 in the elevated motion mode and theseat 22 is in raised position as shown in FIG. 10A, or otherwise to lockthe front arm assembly 38.

The leg 274 is coupled to the arm member 42 proximate the pivot axis P1.As the arm member 42 rotates about the pivot axis P1, the leg 274 andthe plate 290 rotates about pivot axis P1. If the arm member 42 rotatesin a first rotation direction B1, the plate 290 rotates in the secondrotational direction B2 (FIG. 10B). The plate 290 includes a plate body292, a first surface 293, a second surface 294 opposed to the firstsurface 293, and a thickness T (not shown) that extends from the firstsurface 293 to the second surface 294. The plate can define an upperedge 295 and a lower edge 296. The plate is curved as it extends fromthe upper edge 295 to the lower edge 296. In addition, the plate 290defines at least one aperture 272 (FIG. 10D) that extends along adirection aligned or parallel to the thickness T. The aperture 272 issized and configured to receive the pin 276. More specifically, theplate 290 defines an aperture edge 275. The aperture edge 275 definesthe aperture 272. For instance, the aperture 272 can be an elongate slotelongate along a direction that is angularly offset with respect to thethickness either vertically with respect to forward-rearward direction.In other embodiments, the aperture can be circular, oval, or othershaped opening. Further, in alternative embodiments, the plate 290 isconfigured so that the pin 276 can ride along its surface until pin 276extends beyond an edge of the plate 290, such as the aperture edge 275or the lower edge in accordance with certain embodiments.

Continuing with FIGS. 10A-10D, in operation, controller 92 receives aninput to operate wheelchair 210 with the seat 22 in the raised position.In response, the controller 92 the causes the actuator 88 move the pin276 to move into an extended configuration toward the plate 290. Asshown in FIG. 10A, when the plate 290 is in an aligned position wherebythe aperture 272 is aligned with the pin 276, for example due toorientation of the arm member 42 along along flat, level ground G, thepin 276 extends into the aperture 272. When the pin 276 extends alongthe edge 275 into the aperture 272, the arm limiter assembly 260 is inthe locked configuration and movement of the arm member 42 is limited.If, however, the wheelchair 210 is traversing an obstacle O as shown inFIG. 10C and the seat 22 is in the lowered position, the arm member 42is pivoted upwards in a first rotational direction B1 and the plate 290moves downward toward the surface G. This in turn causes the plate 290to slide along the pin 276 such that the pin 276 is disposed adjacentthe surface 294 and positioned upward with respect to aperture edge 275.The plate 290 in this position blocks the pin 276 from extending intothe engaged position. Because the pin 276 is prevented from moving intothe engaged position in the aperture 272, the arm limiter assembly 260is prevented from transitioning into the second or locked configuration.The wheelchair 210 operates similar in some respects as to how thewheelchair 10, 110 operates when the arm limiter assembly 60, 160 isprevented from the transitioning to the locked configuration. Forinstance, the controller 92 may prevent operation of one or more aspectsof the wheelchair 210 in the elevated motion mode, for example, if thecondition of the arm limiter being in the locking condition is not met.After the wheelchair 210 traverses the obstacle O, the arm member 42pivots downwardly until the front wheel 46 and the drive wheels 32 areon flat, level ground as shown in FIGS. 10A and 10B. At this point, theplate 290 is moved upwardly sliding along the pin 276 until the pin 276is aligned with the aperture 272. The pin 276, via the actuator as notedabove, urges the pin 276 to extend along the aperture edge 275 into theaperture 272 placing the arm limiter assembly 260 in the lockedconfiguration. In this regard, the plate 290 is configured as a slidingmember.

The aperture 272 can be elongate along the direction the pin 276 slidesalong the plate 290. In such embodiments, the arm member 42 can pivotthrough the second range of rotation (less than the first range ofrotation) when the arm limiter assembly 260 is in the lockedconfiguration while pin 276 is located in slotted aperture 272. In thisregard, the plate 290 is configured to permit the arm member 42 to pivotup to 4 or 5 degrees away from the its initial position 40 a even whenthe arm limiter 260 is in the locked configuration. This particularembodiment permits the arm assembly 38 to traverse slight obstacles andprevent the arm assembly 38 and the arm limiter assembly 260 fromlocking out, and permits arm assembly 38 to be limited in its downward(direction B2) movement. It should be appreciated, however, that theaperture 272 can have a diameter or other dimension that issubstantially equal to that of the pin 276 such that when the pin 276 isreceived by the aperture 272, the forward extending arm 42 is fixedrelative to the frame 14 with little or no movement.

As illustrated, the aperture 272 is disposed between the upper and lowerplate edges 295 and 296 such that the pin 276 can extend along theaperture edge 275. It should be appreciated, however, that plate 290 canbe configured without an aperture that receives the pint 276. Forinstance, the lower edge 296 can define a surface along which the pin276 extends along in order to transition the arm limiter assembly 260into the second configuration. In other words, the plate 290 can bemoved into the locked or an aligned position when pin 276 is moveablealong the lower edge 296 into its engaged position.

Turning to FIGS. 11A and 11B another embodiment of wheelchair 310 isschematically illustrated including an arm limiter assembly 360according to yet another alternate embodiment of present disclosure. Thepowered wheelchair 310 according to an alternative embodiment of thepresent disclosure is configured similar to the powered wheelchair 10described above. Accordingly, the description below regarding wheelchair310 will use similar reference signs to identify elements common towheelchair 10 and wheelchair 310, such as the frame 14, drive wheels 32(not shown), forward arm assemblies 38, rear arm assemblies 48 (notshown), lift mechanism 18 (not shown), seat 22, and control system 90and sensors.

Continuing with FIGS. 11A and 11B, the arm limiter assembly 360 can beused on any one of the wheelchairs 10, 110, or 210 described above.Further, the wheelchair incorporating arm limiter assembly 360 mayinclude similar components and operation characteristics described aboveexcept as noted otherwise. The arm limiter assembly 360 includes a disc362 or a segment of a disc that is supported by the frame 14 andoperatively engaged with arm assembly 38, and in particular to theproximal end 43 p of the arm member 42. The arm limiter assembly 260includes a caliper or clamp 370 that is supported by the frame 14 of thewheelchair 310 (frame and wheelchair not shown in FIGS. 11A and 11B).The clamp 370 can have a pair of moveable pads 372 a and 372 b spacedapart with respect to each other to define a gap 373. The gap 373 issized to receive a portion of the disc 362 therein such there is nocontact or light contact between the pads 372 a and 372 b and thecorresponding surfaces of disk 362. The clamp 370 is configured toselectively engage the disc 362 to thereby restrict movement of the disc362 and the arm member 42. For instance, the clamp 370 can be coupled tothe actuator 88 such that when the actuator 88 is activated, themoveable arms 372 a, 372 b move toward each other in directions 385 aand 385 b against opposite surfaces 364 and 366 of the disc 362. In afirst or open configuration, the disc 362 is moveable in the gap 373 andthe arm member 42 is moveable through the first range of rotation ormotion. When the wheelchair 310 operates in an elevated motion mode, theactuator 88 closes the clamp 370 tightening against the disc 362.Because the disc 362 is thus fixed to the arm member 42, movement of thearm member 42 is stopped. In an alternative embodiment, the disc 326 canhave a protrusion or stop 368 that is positioned to align between theclamp arms 372 a, 372 b in the gap 373 when the arm member 42 isrotationally different from the first position 40 a by more than 4 or 5degrees. In this position, the disc 362, via the stop 368 in the gap373, prevent the clamp arms 372 a, 372 b from transitioning into theclamped configuration against the surface 364 and 366, which in turnprevents arm limiter assembly 360 from locking movement of the disc andarm member 42.

Turning to FIGS. 12A-12C, a wheelchair 410 is illustrated including anarm limiter assembly 460 according to yet another alternate embodiment.The powered wheelchair 410 is configured similar to the poweredwheelchair 10 described above and illustrated in FIGS. 1-5. Accordingly,the description below regarding wheelchair 410 will use similarreference signs to identify elements common to wheelchair 10 andwheelchair 410, such as the frame 14, drive wheels 32 (not shown),forward arm assemblies 38, rear arm assemblies 48 (not shown), liftmechanism 18 (not shown), seat 22, and control system 90 and sensors. Inthe alternative embodiment, the arm limiter assembly 460 can beconfigured as rear-ward arm limiter assembly.

FIGS. 12A, 12B, 12C schematically illustrate the arm limiter assembly460 in the locking configuration 71C (FIG. 12A), the open configuration71O (FIG. 12B), and a blocked configuration 71B (FIG. 12C), whereby thearm member 42 is preventing transition of the arm limiter assembly 460from the open configuration 71O into the locking configuration 71C. Inthe illustrated embodiment, the arm limiter assembly 460 can beconfigured as rearward arm limiter assembly. The arm limiter assembly460 includes an actuatable unit 462 coupled between the frame 14 and thearm member 42. The actuatable unit 462 can have a housing 464 and anelongate member 466 in the form of a rod or bar that extends out fromthe housing 464 and is movable with respect to the housing 464. FIG. 12Bshows the elongate member 466 in its retracted position. The extendedposition of elongate member 466 is shown in dashed lines in FIG. 12B.The elongate member 466 defines an end 468 spaced from the housing 464along a direction 469 that is aligned with and parallel to the forwarddirection F of the wheelchair 410. The arm limiter assembly 460 has 1) afirst or open configuration, whereby the elongate member 466 isretracted partially into the housing 464 such that the arm member 42 ispivotable through the first range of rotation as discussed above, 2) asecond or locked configuration where the elongate member 466 abuts thestop 44 a of the arm member 42, thereby preventing the arm member 42from pivoting upwardly with respect to the frame 14, and 3) a blockedconfiguration where the arm limiter assembly is prevented fromtransitioning into the locked configuration. The actuatable unit 462 canbe a hydraulic strut, magnetorhealogical strut, gas strut, or otherdevice configured to allow one component to move relative to anothercomponent to selectively engage the arm member 42 as described herein.

Referring first to FIG. 12B, during normal operation and when the seat22 is in the lowered position, the arm limiter assembly 460 is in theopen configuration. The actuator 88 has been actuated to cause theelongate member 466 to retract into the open configuration. Turning toFIG. 12A, when wheelchair 10 is operated in an elevated mode—when theseat 22 is in the raised position—the arm limiter assembly 460transitions into locked configuration such that elongate member 466 isextended to block upward movement of the arm member 42. Accordingly, asthe seat 22 is elevated into the raised position, the forward arm member42 will have a limited range of rotation such that the wheelchair 410 isnot operable to ascend an obstacle O along the surface G. Referring nowto FIG. 12C, if front wheel 46 is on uneven ground surface G relative tothe drive wheels 32, such as when the wheelchair 410 begins ascent ofthe obstacle O, the arm member 42 is pivoted in an upward rotationaldirection B1 away from the first position 40 a into the second position40 b that is rotationally different than the first position 40 a.Because the arm member 42 is pivoted upwards, the stop member 44 a abutsthe forward end 468 of the elongate member 466, preventing furtherprogression of the elongate member 466 into the locking configuration.Once wheelchair 410 has moved to a location on the surface G such thatthe front wheel 46 and the drive wheels 32 are on flat, level ground(i.e. the first position 40 a), the actuatable unit 462 is configured toautomatically urge the elongate member 466 into the lockingconfiguration as shown in FIG. 12A.

Turning to FIGS. 13A and 13B, a powered wheelchair 510 according to analternative embodiment of the present disclosure is configured similarto the powered wheelchair 10 described above and illustrated in FIGS.1-5. Accordingly, the description below regarding wheelchair 510 willuse similar reference numerals to identify elements common to wheelchair10 and wheelchair 510, such as the frame 14, drive wheels 32 (notshown), lift mechanism 18 (not shown), seat 22, and control system 90and sensors. The forward arm assemblies 38 are as described above exceptfor the stop member. In the alternate embodiment, the powered wheelchair510 includes a pair of rearward arm assemblies 548 configured to pivotrelative to the frame 14 between a first position 540 a when thewheelchair is operating on flat, level ground, and any number ofdifferent positions depending on if the wheelchair 510 is ascending anobstacle or initiating a decent down an incline. The rearward armassembly 548 is configured similar to the forward arm assembly 38describe above with reference to FIGS. 1-5 and this paragraph, andincludes an arm member 542, a rear wheel 47 coupled to the arm member542. The arm member 542 can include a stop member 544 a located in thesame place on the arm member 542 as stop member 44 a in poweredwheelchair 10. The stop member 544 a of the arm member 542 in theembodiment shown in FIGS. 13A and 13B is not rounded, but has a verticalcontact face and a horizontal top surface. The rearward arm assembly 548can move in a first rotational direction B1, e.g., upward, when thewheelchair 510 encounters an ascent, or a second rotational directionB1, e.g., downward, when the wheelchair 510 descends down an inclinedsurface.

The powered wheelchair 510 can be configured to limit relative movementof the rearward arm assembly 548 depending on the surface G thewheelchair 510 is operating along. For instance, the arm limiterassembly 560 has an open or first configuration in which the rearwardarm assembly 548 is moveable relative to frame 14 through a first rangeof rotation relative to the pivot axis P1, and a second or lockedconfiguration in which the rearward arm assembly 548 is prevented frommoving relative to the frame 14 as needed. For instance, in the lockedconfiguration, the arm limiter assembly 560 limits movement of the armassembly 546 through a second range of rotation that is less than thefirst range of rotation. It should be appreciated that the second rangeof rotation can include the rearward arm assembly 548 being rotationallyfixed relative to the frame 14. In the with the illustrated embodiment,the arm limiter assembly 560 shown in FIGS. 13A and 13B is configuredsimilar to the actuatable unit type arm limiter assembly 460 describedabove with reference to FIGS. 12A-12C. For example, the arm limiterassembly 560 includes an actuatable unit 562 coupled between the frame14 and the arm member 42. The actuatable unit 562 can have a housing 564and an elongate member 566 in the form of a rod or bar that extends outfrom the housing 564 and is movable with respect to the housing 564.FIG. 13B shows the elongate member 566 in its retracted position.However, it should be appreciated that wheelchair 510 can include anyoneof the arm limiter assemblies 60, 160, 260, and 360 as described above,or the arm limiter assemblies 660, 760, 860, or 760 described below.

Turning to FIGS. 14A and 14B, a wheelchair 710 is illustrated includingan arm limiter assembly 760 according to yet another alternateembodiment. The powered wheelchair 710 is configured similar to thepowered wheelchair 10 described above and illustrated in FIGS. 1-5.Accordingly, the description below regarding wheelchair 710 will usesimilar reference signs to identify elements common to wheelchair 10 andwheelchair 710, such as the frame 14, drive wheels 32 (not shown),forward arm assemblies 38, rear arm assemblies 48 (not shown), liftmechanism 18 (not shown), seat 22, and control system 90 and sensors. Inaccordance with the alternative embodiment, the arm limiter assembly 760can be configured as rear-ward arm or forward arm limiter assembly asnoted above.

FIGS. 14A and 14B schematically illustrates operation of the arm limiterassembly 760. The arm limiter assembly 760 can have a first or openconfiguration where the arm member 42 has a first range of rotation, anda second or locked configuration where the arm member has a second rangeof rotation that is smaller than the first range of rotation. The armlimiter assembly 760 can include an actuatable unit 770 and an actuator88. The wheelchair 710 can further include one or more the arm positionsensors described above to detect the position of the arm member 42relative the frame 14. The actuatable unit 770 is coupled to the frame14 and the arm member 42.

Continuing with FIGS. 14A and 14B, the actuatable unit 770 can beconfigured as a strut and may include a first component or housing 772and a second component or piston 774 moveably coupled to the firstcomponent 772. The second component includes a rod or bar that extendsout from the housing 772 and is movable with respect to the housing 772.The strut 770 includes proximal end (not numbered) and a distal end (notnumbered) spaced from the proximal end along the axis 71. The proximalend of the strut 770 is pivotably coupled to frame 14 via connector 776.The distal end of the strut 770 is pivotably coupled to arm member 42via connector 778. The pivotable connections between the actuatable unit770 and the arm member 42 and frame 14 account for the pivotableconnection of the arm member 42 to the frame 14 as illustrated. Fortranslating type arm members (See FIGS. 15A and 15B), it should beappreciated that the actuatable unit 770 may be pivotably connected tothe frame 14 only. Further, the actuatable unit 770 defines a length 780that extends from a point defined by connector 776 to the point (notshown) defined by connector 778. As the arm member 42 pivots upwardlyaway from the first position 40 a (FIG. 14A) into the second position 40b (FIG. 14B), the length 780 decreases to a second, shorter length 780′.If the arm member 42 pivots downwardly away from the position 40 a, thelength 780 will increase. During normal operation when the seat is inthe lowered position, the actuatable unit 770 is in the first or openconfiguration such that its length 780 can be adjusted to account formovement of the arm member 42 in an upward and downward direction. Whenthe seat is moved into the raised configuration, the actuator 88 cancause the strut to lock or increase resistance to length adjustment,thereby inhibiting the ability of the actuatable unit 770 to compress orretract based on the position of the arm member 42. The actuatable unit770 can be a hydraulic strut, magnetorhealogical strut, gas strut, orother device configured to allow one component to move relative toanother component to selectively engage the arm member as describedherein.

Turning to FIGS. 15A-15C, an alternative embodiments of a poweredwheelchair 810. In the embodiment shown in FIGS. 15A-15C, poweredwheelchair 810 is configured similar to the powered wheelchair 10described above and illustrated in FIGS. 1-5. Accordingly, thedescription below regarding wheelchair 610 will use similar referencenumerals to identify elements common to wheelchair 10 and wheelchair810, such as the frame 14, drive wheels 32 (not shown), lift mechanism18 (not shown), seat 22, arm assembly 38, control system 90 and sensors.In the illustrated embodiments, the powered wheelchair includes an armlimiter assembly 860 configured to progressively restrict the range ofrotation which the arm member 42 and wheel axis A1. The arm limiterassembly 860 includes a rotatable member 870 rotatably mounted to theframe 14, an actuator 88, a transfer linkage 84 coupled to actuator 88,and a biasing member, such as spring 80 operably connected to thelinkage 84 and the rotatable member 870. The actuator 88 is operable tocause movement of the transfer linkage 84, which in turn causes movementof the rotatable member 870 similar to the embodiment of the arm limiterassembly 60 described above.

Continuing with FIG. 15A, the rotatable member 870 is configured as acam and defines a body 874 having a proximal end 874 a rotatably coupledto the frame 14 at pivot axis P2, and a distal end 874 b opposed toproximal end 874 a along an axis 71. The proximal end 874 a is rotatablycoupled to the frame 14 at pivot axis P2. The body 874 includes aforward edge 875 a and a rearward edge 875 b opposed to the forward edge875 a. The body 874 defines a curved distal edge 878. As illustrated,the curved distal edge 878 includes a surface that is curved withrespect to the axis 71 as it extends from the forward edge 875 a to therearward edge 875 b. The curved distal edge 878 is configured toselectively engage the stop member 44 a depending on the rotationalposition of the rotatable member 870 about pivot axis P1 and theposition of the arm member 42.

As illustrated, the curved distal edge 878 progressively restricts therange of rotation (or motion) which the arm member 42 can move relativeto the frame 14. For instance, when the rotatable member 870 is in afirst orientation 879 a, the rotatable member 870 permits the arm member42 to move through a first range of rotation that is equivalent to fullrange of movement of the arm member 42 and wheel axis A1 relative to theframe 14. As shown in FIG. 15A, the distal contact edge 878 isdisengaged from the arm member 42 when the rotatable member 870 is inthe first orientation 879 a.

As shown in FIG. 15B, when the rotatable member 870 is in a secondrotational orientation 879 b that is slightly offset in a rotationaldirection (e.g. clockwise in FIGS. 3A-4D) with respect to the firstrotational orientation 879 a, the distal contact surface 878 is advancedforward to engage the stop member 44 a when the arm member 42 is in aselect positioned that may or may not be the first position 40 a asdescribed above. In the second rotational orientation 879 b, therotatable member 870 permits the arm member 42 to move through a secondrange of rotation that is less than the first range of rotation. Asshown in FIG. 15C, when the rotatable member 870 is in a thirdrotational orientation 879 c that is further offset clockwise withrespect to the second rotational orientation 897 b, the rotatable member870 permits the arm member 42 to move through a third range of rotationthat is less than the second range of rotation. In the thirdorientation, the distal contact surface 878 is further advance so thatthe portion of the contact surface rearward of the axis 71 abuts thestop member 44 a. As shown comparing FIGS. 15A and 15B, the orientationof the rotatable member can limit the ability of the arm assembly toascend an obstacles of difference elevations. The actuator 88 andbiasing member 80 can control orientation of the rotatable member 870.For instance, if the controller receives an instruction to raise theseat, a control signal is sent the actuator 88. In response the controlsignal, the actuator 88 urges the rotatable member 870 into a desiredorientation.

Turning to FIGS. 16A and 16B, an alternative embodiments of a poweredwheelchair 610, the arm assembly 638 can be configured such that the armmember 42 and wheel axis A1 is translatable from the first position 40 ato the second position 40 b. In the embodiment shown in FIGS. 16A and16B, powered wheelchair 610 is configured similar to the poweredwheelchair 10 described above and illustrated in FIGS. 1-5. Accordingly,the description below regarding wheelchair 610 will use similarreference numerals to identify elements common to wheelchair 10 andwheelchair 610, such as the frame 14, drive wheels 32 (not shown), liftmechanism 18 (not shown), seat 22, arm limiter assembly 60, controlsystem 90 and sensors. In the alternate embodiment, the poweredwheelchair 610 includes a pair of forward arm assemblies 638 moveablycoupled to a track 650 that extends forwardly from the frame 14. Thetrack 650 receives the proximal end 43 p (shown in dashed lines in FIGS.16A and 16B) of the arm member 42. As illustrated, the proximal end 43 pis slidable within the track 650 via a bearing or roller mechanism (notshown) so that arm member 42 and wheel 46 are translatable along thetrack 650 upwardly or downwardly relative to the frame 14 in a lineardirection C. The linear direction C can extend along the verticaldirection V or may be angularly offset (as illustrated) with respect thevertical direction V. Accordingly, the arm assemblies 638 are coupled tothe frame 14 such that the wheel 46 is translatable from between thefirst position 40 a and the second position 40 a depending on theobstacle the wheel 46 is traversing. As noted above, operation of thearm assembly 638 is similar to operation of the arm assembly as the 008patent noted above. The disclosure of the 008 patent is incorporated byreference herein for all purposes.

Continuing with FIGS. 16A and 16B, in alternative embodiments when thearm limiter assembly 60 is in the disengaged or open configuration thearm member 42 is translatable from the first position 40 a through afirst range of motion. When the arm limiter assembly 60 is in theengaged or locked configuration, the arm member 42 is translatablethrough a second range of motion that is less than the first range ofmotion. While arm member 42 is translatable along the linear directionC, the positional difference of the wheel 46 in the first and secondpositions 40 a and 40 b can have an angular component. The firstposition 40 a in FIG. 16A can be defined by first reference and secondlines (not shown) that intersect the front wheel axis A1 and aforward-most point (651) located on the bottom 14 b of the frame 14.When the arm assembly 638 translates the wheel 46 from the firstposition 40 a to the second position 40 b, the second reference linedefines an angle α1 (not shown) with the first reference line (notshown). Accordingly, the range of motion as described with respect towheelchair 16 can correspond to range of rotation described with respectto the wheelchair 10.

The safety features described in present disclosure are not limited tothe powered wheelchair configurations specifically disclosed andillustrated in the accompanying drawings. The wheelchair as describedherein can include any one of the arm limiter assemblies 60, 160, 260,360, 460, 560, and 610 described herein, a forward arm assemblymoveably, i.e. rotatably and/or translatably, coupled to the frame 14,and a rearward arm assembly moveable coupled to the frame 14. Morespecifically, such a wheelchair includes a forward arm member 42 and arearward arm member 49 (see FIG. 2A) that are both moveable relative tothe frame such that the front wheel 46 and rear wheel 49, respectively,are moveable relative to the frame 14 away (upwardly or downwardly) fromtheir respective first or rest positions. Movement of the wheels 46 and49 away from the first positions are dependent on the features on theground G that wheelchair is traversing. In certain embodiments, theforward arm member 42 and the rearward arm members 49 can be linked,directly or indirectly, such that movement of one arm member causesmovement of the other arm member. In such an embodiment, arm limiterassemblies 60, 160, 260, 360, 560, and 610 as described hereinselectively permit or prevent movement of 1) the forward arm member 42,2) the rearward arm member 49, or 3) both the forward and rearward armmember 49 upwardly or downwardly with respect to the first position ofeach respective wheel 46 and 47. More specifically, any one of armlimiter assemblies 60, 160, 260, 360, 560, and 610 can be positionedtoward the front 14 f of the frame 14 to selectively inhibit movement ofthe front arm assembly 38. And because the forward arm member 42 islinked to the rear arm member 49, when the front arm member 42 has alimited range of motion due to engagement with the arm limiter assembly,the rear arm member 49 has a limited range of motion as well. Thereverse is contemplated—that the arm limiter assembly engaged with reararm member 47 and limiting its range of motion also limits the range ofmotion of the forward arm member 42. In addition, if one of the frontarm member 42 or the rear arm member 49 is moved out of its first orrest position prior to the arm limiter assembly transitioning into thelocking configuration, stop members along each arm member 42 or 49inhibits the arm limiter assembly from transitioning into the lockedconfiguration. When the wheelchair returns to flat, level ground, thefront and rear arm members 42 and 49 return to the first position andthe arm limiter assembly transitions into the locking configuration.

Various embodiments of wheelchairs have been described. It should beappreciated that the features and elements from one wheelchair can becombined with features and elements of another wheelchair. For instance,any wheelchair 10, 110, 210, 310, 410, 510, 610, 710, 810 may includeany one of the arm limiter assemblies 60, 160, 260, 360, 460, 560, 660,760, or 860. Further, any components for each arm limiter assemblies 60,160, 260, 360, 460, 560, 660, 760, or 860 may be combined with othercomponents from each arm limiter assembly 60, 160, 260, 360, 460, 560,660, 760, or 860, as needed.

While the foregoing description and drawings represent the variousexemplary embodiments of the present disclosure, it will be understoodthat various additions, modifications, combinations and/or substitutionsmay be made therein without departing from the spirit and scope of theinvention as defined in the accompanying claims. In particular, it willbe clear to those skilled in the art that the invention may be embodiedin other specific forms, structures, arrangements, proportions, and withother elements, materials, and components, without departing from thespirit or essential characteristics thereof. One skilled in the art willappreciate that the invention may be used with many modifications ofstructure, arrangement, proportions, materials, and components, whichare adapted to specific environments and operative requirements withoutdeparting from the principles of the invention. In addition, featuresdescribed herein may be used singularly or in combination with otherfeatures. For example, features described in connection with onecomponent or embodiment may be used and/or interchanged with featuresdescribed in another component or embodiment. The presently disclosedembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims, and not limited to the foregoingdescription.

What is claimed:
 1. A powered wheelchair comprising: a frame; a liftmechanism supported by the frame: a seat supported by the liftmechanism, the lift mechanism configured to move the seat from a loweredposition to a raised position; a pair of drive wheels; at least onedrive coupled to the frame and configured to apply a torque to at leastone wheel of the pair of drive wheels; an arm assembly including an armmember pivotably coupled to the frame; a front wheel rotatably coupledto the arm member; and an arm limiter assembly including an arm limiter,the arm limiter assembly coupled to the frame and configured to movefrom a first configuration whereby the arm member is capable of pivotingrelative to the frame through a first range of rotation that isuninhibited by the arm limiter assembly, to a second configurationwhereby the arm member is capable of pivoting relative to the framethrough a second range of rotation that is inhibited by the arm limiterassembly when the arm member abuts the arm limiter, wherein the armlimiter is configured to compress in response to upward movement of thearm member, such that the second range of rotation is smaller than thefirst range of rotation.
 2. The powered wheelchair of claim 1, whereinat least a portion of the arm limiter is configured to at leastpartially compress in response to upward movement of the arm member. 3.The powered wheelchair of claim 2, wherein the portion of the armlimiter that is configured to at least partially compress includes abiasing element.
 4. The powered wheelchair of claim 1, wherein the armlimiter comprises a proximal portion and a distal portion spaced fromthe proximal portion along an axis that extends in a distal direction.5. The powered wheelchair of claim 4, further comprising a biasingelement that is disposed at least partially between the proximal portionand the distal portion of the arm limiter.
 6. The powered wheelchair ofclaim 5, wherein the biasing element is configured to at least partiallycompress in response to upward movement of the arm member when thedistal portion of the arm limiter abuts the arm member.
 7. The poweredwheelchair of claim 5, wherein the distal portion of the arm limitercomprises a translating member.
 8. The powered wheelchair of claim 7,wherein the biasing element is coupled to the translating member.
 9. Thepowered wheelchair of claim 7, wherein the translating member istranslatable in a proximal direction toward the proximal portion of thearm limiter and away from the proximal portion in the distal direction.10. The powered wheelchair of claim 7, wherein the translating memberdefines at least one outer surface configured to engage the arm member.11. The powered wheelchair of claim 10, wherein the at least one outersurface comprises a forward surface portion, a rearward surface portionopposite the forward surface portion along a transverse direction thatis perpendicular to the axis, and a distal-most surface portion thatextends from the forward surface portion to the rearward surfaceportion.
 12. The powered wheelchair of claim 11, wherein the distal-mostsurface portion of the translating member is configured to abut the armmember when the arm limiter assembly is in the second configuration. 13.The power wheelchair of claim 11, wherein the forward surface portiondefines an inclined surface at an oblique angle with respect to the axisand the transverse direction, the rearward surface portion defines asurface that is substantially parallel with the axis, and thedistal-most surface is substantially perpendicular to the axis.
 14. Thepowered wheelchair of claim 11, wherein the forward surface portion issubstantially parallel to the axis and the distal-most surface portiondefines a declined surface at an oblique angle with respect to the axisand the transverse direction.
 15. The powered wheelchair of claim 10,wherein the at least one outer surface defines a distal surface that iscurved with respect to the axis and is inclined along a transversedirection that is perpendicular to the axis.
 16. The powered wheelchairof claim 10, wherein the at least one outer surface comprises ahemispherical surface.
 17. The powered wheelchair of claim 10, whereinthe at least one outer surface defines a distal surface that is curvedwith respect to the axis.
 18. The powered wheelchair of claim 10,further comprising a stop member coupled to the arm member, wherein theat least one outer surface of the translating member is configured toengage the stop member.
 19. The powered wheelchair of claim 10, whereinthe proximal portion of the arm limiter comprises a body that isconfigured to support the translating member and the biasing element.20. The powered wheelchair of claim 19, wherein the translating memberincludes a connection member that is movably coupled to the body. 21.The powered wheelchair of claim 20, wherein the body defines a proximalend, a forward side, a rearward side opposed to the forward side along atransverse direction that is perpendicular to the axis, and a centerportion disposed between the forward and rearward sides, the centerportion including a channel aligned along the axis and configured toreceive the connection member; and the connection member is translatablewithin the channel along the axis in a proximal direction toward theproximal end of the body and in the distal direction away from theproximal end of the body.
 22. The powered wheelchair of claim 10,wherein the proximal portion of the arm limiter includes a connectionmember; and the translating member comprises a body that is movablycoupled to the connection member.
 23. The powered wheelchair of claim22, wherein the body defines a forward side, a rearward side opposed tothe forward side along a transverse direction that is perpendicular tothe axis, and a center portion disposed between the forward and rearwardsides, the center portion including a channel aligned along the axis andconfigured to receive the connection member; and the body istranslatable along the connection member in a proximal direction towardthe proximal portion of the arm limiter and in the distal direction awayfrom the proximal portion.
 24. The powered wheelchair of claim 5,wherein the biasing element comprises one or more of a spring, ahydraulic cylinder, and a compressible material.